The BKG Ntrip Client (BNC) is a program for simultaneously retrieving, decoding, converting and processing or analyzing real-time GNSS data streams applying the 'Networked Transport of RTCM via Internet Protocol' (Ntrip) standard. It has been developed within the framework of the IAG sub-commission for Europe (EUREF) and the International GNSS Service (IGS). Although meant as a real-time tool, it comes with some Post Processing functionality. You may like to use it for data coming from Ntrip Broadcasters like

• http://www.euref-ip.net/home,
• http://www.igs-ip.net/home,
• http://products.igs-ip.net/home,
• http://mgex.igs-ip.net/home.

BNC has been written under GNU General Public License (GPL). Source code is available from Subversion software archive http://software.rtcm-ntrip.org/svn/trunk/BNC. Binaries for BNC are available for Windows, Linux, and Mac OS X systems. We used the MinGW Version 4.4.0 compiler to create the Windows binaries. It is likely that BNC can be compiled on other systems where a GNU compiler and Qt Version 4.8.4 or any later version are installed. Please ensure that you always use the latest precompiled version of BNC available from http://igs.bkg.bund.de/ntrip/download. Note that static and shared builds of BNC are made available. A static build would be sufficient in case you don't want BNC to trace PPP results using Google Map (GM) or OpenStreetMap (OSM). However, GM/OSM usage requires the QtWebKit library which can only be part of BNC builds from shared libraries. Using a shared library BNC build requires that you first install your own shared Qt library. The 'README.txt' file which comes with the BNC source code describes how to install Qt on Windows, Linux and Mac systems.

Feel free to send us comments, suggestions or bug reports. Any contribution would be appreciated.

   Prof. Dr. Leos Mervart
   Czech Technical University (CTU)
   Department of Geodesy
   Prague, Czech Republic

Prof. Mervart started working on BNC in 2005. His sole responsibility for writing the program code ended February 2015. Since March 2015 the expert in charge at BKG for further BNC programming is Dipl.-Ing. Andrea Stürze [andrea.stuerze@bkg.bund.de].

BNC provides context-sensitive online help (What's This) related to specific objects. It furthermore comes with the here presented documentation, available as an integral part of the software and as a PDF file. Responsible for online and offline documentation, example configurations (and till February 2014 the overall BNC policy concept) is Dr. Georg Weber [georg.weber@bkg.bund.de].

BNC includes the following GNU GPL software components:

• RTCM 2 decoder, written by Oliver Montenbruck, German Space Operations Center, DLR, Oberpfaffenhofen, Germany;
• RTCM 3 decoder for conventional and MSM observation messages and a RTCM 3 encoder & decoder for SSR messages, both written for BKG by Dirk Stoecker, Alberding GmbH, Schoenefeld, Germany.

Note that some figures presented in this documentation may show screenshots from earlier versions of BNC. If so then there is either no relevant change compared to the current appearance of the program or no change at all.

Acknowledgements

• Thomas Yan, Australian NSW Land and Property Information, proofread earlier versions of BNC's Help Contents. Up to Version 2.11 he also provides builds of BNC for Mac OS X systems.
• Scott Glazier, OmniSTAR Australia, has been helpful in finding BNC bugs in version 1.5.
• James Perlt, BKG, helped fixing bugs and redesigned BNC's main window in version 1.5.
• Andre Hauschild, German Space Operations Center, DLR, revised the RTCM Version 2 decoder.
• Zdenek Lukes, Czech Technical University Prague, Department of Geodesy, extended the RTCM Version 2 decoder to handle message types 3, 20, 21, and 22 and added the loss of lock indicator.
• Jan Dousa, Geodetic Observatory Pecny, Czech Republic, helped with fixing bugs in version 2.5.
• Denis Laurichesse, Centre National d'Etudes Spatiales (CNES), suggested synchronizing observations and clock corrections to reduce high frequency noise in PPP solutions.
• Lennard Huisman, Kadaster Netherlands, and Rolf Dach, Astronomical Institute University of Bern, assisted in handling satellite clocks in transformations from ITRF to regional reference frames.

The purpose of BNC is to

• Retrieve real-time GNSS data streams available through Ntrip transport protocol;
• Retrieve real-time GNSS data streams via TCP directly from an IP address without using the Ntrip transport protocol;
• Retrieve real-time GNSS data streams from a local UDP or serial port without using the Ntrip transport protocol;
• Plot stream distribution map from Ntrip Broadcaster source-tables;
• Generate RINEX Observation and Navigation files to support near real-time GNSS Post Processing applications;
• Edit or concatenate RINEX files or carry out RINEX Quality Checks (QC);
• Convert RINEX Version 2 to RINEX Version 3 and vice versa;
• Compare SP3 files containing satellite orbit and clock data;
• Generate orbit and clock corrections to Broadcast Ephemeris through an IP port to
• support real-time Precise Point Positioning on GNSS rovers;
• support the (outside) combination of such streams as coming simultaneously from various correction providers;
• Generate ephemeris and synchronized or unsynchronized observations epoch by epoch through an IP port to support real-time GNSS network engines;
• Feed a stream into a GNSS receiver via serial communication link;
• Monitor the performance of a network of real-time GNSS data streams to generate advisory notes in case of outages or corrupted streams;
• Scan RTCM streams for incoming antenna information, observation types, message types and repetition rates and latencies and GLONASS slot numbers and frequency channels;
• Carry out real-time Precise Point Positioning to determine GNSS rover positions;
• Enable multi-station Precise Point Positioning for simultaneous processing of observations from a whole network of receivers;
• Plot positions derived via PPP from RTCM streams or RINEX files on maps from Google Map or OpenStreetMap;
• Simultaneously process several Broadcast Correction streams to produce, encode and upload combined Broadcast Corrections;
• Read GNSS orbits and clocks in a plain ASCII format from an IP port. They can be produced by a real-time GNSS engine such as RTNET and should be referenced to the IGS Earth-Centered-Earth-Fixed (ECEF) reference system. BNC will then
• Convert the IGS Earth-Centered-Earth-Fixed orbits and clocks into Broadcast Corrections with radial, along-track and cross-track components;
• Upload Broadcast Corrections as an RTCM Version 3 stream to an Ntrip Broadcaster;
• Refer the orbit and clock corrections to a specific reference system;
• Log the Broadcast Corrections as Clock RINEX files for further processing using other tools than BNC;
• Log the Broadcast Corrections as SP3 files for further processing using other tools than BNC;
• Upload a Broadcast Ephemeris stream in RTCM Version 3 format;

BNC supports the following GNSS stream formats and message types:

• RTCM Version 2 message types;
• RTCM Version 3 'conventional' message types;
• RTCM Version 3 message types for Broadcast Ephemeris;
• RTCM Version 3 'State Space Representation' (SSR) messages;
• RTCM Version 3 'Multiple Signal Messages' (MSM) and 'High Precision Multiple Signal Messages' (HP MSM);
• RTNET, a plain ASCII format defined within BNC to receive orbits and clocks from a serving GNSS engine.

Note that BNC allows to by-pass its decoding and conversion algorithms for incoming streams, leave whatever is received untouched to save it in files or output it through local TCP/IP port.

BNC is permanently completed to finally support all existing GNSS systems throughout all features of the program. The table below shows in detail which GNSS systems are so far supported by particular applications when using the latest BNC version. Application areas named here are:

• Decoding of RTCM or RTNET streams
• RINEX and SP3 file input and output
• Encoding of SSR and ephemeris messages
• Upload of SSR and ephemeris messages
• PPP (Precise Point Positioning)
• Combining/merging SSR or ephemeris messages from various real-time sources

Table 1: Status of RTCM Version 3 message implementations in BNC supporting various GNSS systems

BNC can be used in different contexts with varying data flows. Typical real-time communication follows the Ntrip protocol over TCP/IP (probably via SSL), RTSP/RTP or UDP, plain TCP/IP protocol, or serial communication links. Stream contents could be observations, ephemeris, satellite orbit/clock products or NMEA sentences.

The first of the following figures shows a flow chart of BNC connected to a GNSS receiver providing observations via serial or TCP communication link for the purpose of Precise Point Positioning. The second figure shows the conversion of RTCM streams to RINEX files. The third figure shows a flow chart of BNC feeding a real-time GNSS engine which estimates precise orbits and clocks. BNC is used in this scenario to encode correctors to RTCM Version 3 and upload them to an Ntrip Broadcaster. The fourth figure shows BNC combining several Broadcast Correction streams to disseminate the combination product while saving results in SP3 and Clock RINEX files.

Figure 1: Flowchart, BNC connected to a GNSS rover for Precise Point Positioning.

Figure 2: Flowchart, BNC converting RTCM streams to RINEX batches.

Figure 3: Flowchart, BNC feeding a real-time GNSS engine and uploading encoded Broadcast Corrections.

Figure 4: Flowchart, BNC combining Broadcast Correction streams.

Although BNC is mainly a real-time tool to be operated online, it can be run offline

• To simulate real-time observation situations for debugging purposes;
• For Post Processing purposes.

Unless it runs offline, BNC

• Requires access to the Internet with a minimum of about 2 to 6 kbits/sec per stream depending on the stream format and the number of visible satellites. You need to make sure that the connection can sustain the required bandwidth;
• Requires the clock of the host computer to be properly synchronized;
• Has the capacity to retrieve hundreds of GNSS data streams simultaneously. Please be aware that such usage may incur a heavy load on the Ntrip Broadcaster side depending on the number of streams requested. We recommend limiting the number of streams where possible to avoid unnecessary workload.

The main window of BNC shows a 'Top menu bar' section, a 'Settings' sections with panels to set processing options, a 'Streams' section, a section for 'Log' tabs, and a 'Bottom menu bar' section, see figure below.

Figure 5: Sections on BNC's main window.

Running BNC in interactive mode requires graphics support. This is also required in batch mode when producing plots. Windows and Mac OS X systems always support graphics. However, when using BNC in batch mode on Linux systems for producing plots, you need to make sure that at least a virtual X-Server like 'Xvfb' is installed and the '-display' command-line option is used.

The usual handling of BNC is that you first select a number of streams ('Add Stream'). Any stream configured to BNC shows up on the 'Streams' canvas in the middle of BNC's main window. You then go through BNC's various configuration panels to set a combination of input, processing and output options before you start the program ('Start'). Most configuration panels are dedicated to a certain functionality of BNC. If the first option field on such a configuration panel is empty, the affected functionality is deactivated.

The following sections present information on how the BNC configuration works and provide configuration examples which can be adjusted according to specific user needs.

As a default, configuration files for running BNC on Unix/Linux/Mac OS X systems are saved in directory '${HOME}/.config/BKG'. On Windows systems, they are typically saved in directory 'C:/Documents and Settings/Username/.config/BKG'. The default configuration filename is 'BNC.bnc'.

The default filename 'BNC.bnc' can be changed and the file contents can easily be edited. On graphical user interfaces it is possible to Drag & Drop a configuration file icon to start BNC (not on Mac OS X systems). Some configuration options can be changed on-the-fly. See annexed 'Configuration List' for a complete set of configuration options. It is also possible to start and configure BNC via command line.

BNC maintains configuration options at three different levels:

1. GUI, input fields level
2. Active configuration level
3. Configuration file, disk level

Figure 6: Management of configuration options in BNC:

	Left:	BNC in graphics mode; active configuration options are introduced through GUI input fields and finally saved on disk.
	Middle:	BNC in 'no window' mode; active configuration options are read from disk.
	Right:	BNC in 'no window' mode without configuration file; default configuration options can be replaced via command line options.

Configuration options are usually specified using GUI input fields (1) after launching BNC. When hitting the 'Start' button, configuration options are transferred one level down to become BNC's active configuration (2), allowing the program to begin its operation. Pushing the 'Stop' button ends data processing so that the user can finally terminate BNC through 'File'->'Quit'->'Save Options' which saves processing options in a configuration file to disk (3). It is important to understand that:

• Active configuration options (2) are independent from GUI input fields and configuration file contents.
• Hence changing configuration options at GUI level (1) while BNC is already processing data does not influence a running job.
• Editing configuration options at disk level (3) while BNC is already processing data does also not influence a running job. However, there are two exceptions which force BNC to update certain active options on-the-fly:
• Pushing the 'Reread & Save Configuration' button lets BNC immediately reread its configuration from GUI input fields to make them active configuration options. Then BNC saves them on disk.
• Specifying the 'Reread configuration' option lets BNC reread its configuration from disk at pre-defined intervals.
• A specific BNC configuration can be started in 'no window' mode from scratch without a configuration file if options for the active configuration level (2) are provided via command line.

BNC comes with a number of configuration examples which can be used on all operating systems. Copy the complete directory 'Example_Configs' which comes with the software including sub-directories 'Input' and 'Output' to your disc. There are two ways to start BNC using one of the example configurations:

• On graphical systems (except for Mac systems) you may use the computer mouse to 'drag' a configuration file icon and 'drop' it on top of BNC's program icon.
• On non-graphical systems or when running BNC in batch mode in the background you may start the program using a command line with the following option for a configuration file (example for Windows systems):
  bnc.exe --conf <configFileName> --nw

Although it's not a must, we suggest that you always create BNC configuration files with the filename extension '.bnc'.

We furthermore suggest for convenience reasons that you configure your system to automatically start BNC when you double-click a file with the filename extension '.bnc'. The following describes what to do on Windows systems to associate the BNC program to such configuration files:

1. Right-click a file that has the extension '.bnc' and then click 'Open'. If the 'Open' command is not available, click 'Open With' or double-click the file.
2. Windows displays a dialog box that says that the system cannot open this file. The dialog box offers several options for selecting a program.
3. Click 'Select the program from a list', and then click 'OK'.
4. The 'Open With' dialog box is displayed. Click 'Browse', locate and then click the BNC program, and then click 'Open'.
5. Click to select the 'Always use the selected program to open this kind of file' check box.
6. Click 'OK'.

Some of the presented example configuration files contain a user ID 'Example' with a password 'Configs' for accessing a few GNSS streams from public Ntrip Broadcasters. This generic account is arranged for convenience reasons only. Please be so kind as to replace the generic account details as well as the place holders 'User' and 'Pass' by the personal user ID and password you receive following an online registration through http://register.rtcm-ntrip.org.

Note that the account for an Ntrip Broadcaster is usually limited to pulling a specified maximum number of streams at the same time. As running some of the example configurations requires pulling several streams, it is suggested to make sure that you don't exceed your account's limits.

Make also sure that sub-directories 'Input' and 'Output' which are part of the example configurations exist on your system or adjust the affected example configuration options according to your needs.

Some BNC options require antenna phase center variations as made available from IGS through so-called ANTEX files at ftp://igs.org/pub/station/general. An example ANTEX file 'igs08.atx' is part of the BNC package for convenience.

The example configurations assume that no proxy protects your BNC host. Should a proxy be operated in front of BNC then you need to introduce its IP and port in the 'Network' panel.

You should be able to run all configuration examples without changing their options. However, configurations 'Upload.bnc' and 'UploadPPP.bnc' are exceptions because they require an input stream from a connected network engine.

1. File 'RinexObs.bnc'
   The purpose of this configuration is showing how to convert RTCM streams to RINEX Observation files. The configuration pulls streams from Ntrip Broadcasters using Ntrip version 1 to generate 15min 1Hz RINEX Version 3 Observation files. See http://igs.bkg.bund.de/ntrip/observations for observation stream resources.


2. File 'RinexEph.bnc'
   The purpose of this configuration is showing how to convert a RTCM stream carrying navigation messages to a RINEX Navigation files. The configuration pulls an RTCM Version 3 stream with Broadcast Ephemeris coming from the real-time EUREF and IGS networks. It saves hourly RINEX Version 3 Navigation files. See http://igs.bkg.bund.de/ntrip/ephemeris for further real-time Broadcast Ephemeris resources.


3. File 'BrdcCorr.bnc'
   The purpose of this configuration is to save Broadcast Corrections from RTCM SSR messages in a plain ASCII format as hourly files. See http://igs.bkg.bund.de/ntrip/orbits for further real-time IGS or EUREF orbit/clock products.


4. File 'RinexConcat.bnc'
   The purpose of this configuration is to concatenate RINEX Version 3 files to produce a concatenated file and edit the marker name in the file header. The sampling interval is set to 30 seconds. See section 'RINEX Editing & QC' in the documentation for examples on how to call BNC from command line in 'no window' mode for RINEX file editing, concatenation and quality checks.


5. File 'RinexQC.bnc'
   The purpose of this configuration is to check the quality of a RINEX Version 3 file through a multipath analysis. The results is saved in disk in terms of a plot in PNG format. See section 'RINEX Editing & QC' in the documentation for examples on how to call BNC from command line in 'no window' mode for RINEX file editing, concatenation and quality checks.


6. File 'RTK.bnc'
   The purpose of this configuration is to feed a serial connected receiver with observations from a reference station for conventional RTK. The stream is scanned for RTCM messages. Message type numbers and latencies of incoming observation are reported in BNC's logfile.


7. File 'FeedEngine.bnc'
   The purpose of this configuration is to feed a real-time GNSS engine with observations from a remote reference stations. The configuration pulls a single stream from an Ntrip Broadcasters. It would of course be possible to pull several streams from different casters. Incoming observations are decoded, synchronized and output through a local IP port and saved into a file. Failure and recovery thresholds are specified to inform about outages.


8. File 'PPP.bnc'
   The purpose of this configuration is Precise Point Positioning from observations of a rover receiver. The configuration reads RTCM Version 3 observations, a Broadcast Ephemeris stream and a stream with Broadcast Corrections. Positions are saved in the logfile.


9. File 'PPPNet.bnc'
   The purpose of this configuration is to demonstrate simultaneous Precise Point Positioning for several rovers or several receivers from a network of reference stations in one BNC job. The possible maximum number of PPP solutions per job depends on the processing power of the hosting computer. This example configuration reads two RTCM Version 3 observation streams, a Broadcast Ephemeris stream and a stream with Broadcast Corrections. PPP Results for the two stations are saved in PPP logfiles.


10. File 'PPPQuickStart.bnc'
    The purpose of this configuration is Precise Point Positioning in Quick-Start mode from observations of a static receiver with precisely known position. The configuration reads RTCM Version 3 observations, Broadcast Corrections and a Broadcast Ephemeris stream. Positions are saved in NMEA format on disc. Positions are also output through IP port for real-time visualization with tools like RTKPLOT. Positions are also saved in the logfile.


11. File 'PPPPostProc.bnc'
    The purpose of this configuration is Precise Point Positioning in Post Processing mode. BNC reads a RINEX Observation and a RINEX Version 3 Navigation files and a Broadcast Corrections file. PPP processing options are set to support the Quick-Start mode. The output is saved in a specific Post Processing logfile and contains the coordinates derived over time following the implemented PPP filter algorithm.


12. File 'PPPGoogleMaps.bnc'
    The purpose of this configuration is to track BNC's point positioning solution using Google Maps or OpenStreetMap as background. BNC reads a RINEX Observation file and a RINEX Navigation file to carry out a 'Standard Point Positioning' solution in post-processing mode. Although this is not a real-time application it requires the BNC host to be connected to the Internet. Specify a computation speed, then hit button 'Open Map' to open the track map, then hit 'Start' to visualize receiver positions on top of GM/OSM maps.


13. File 'SPPQuickStartGal.bnc'
    The purpose of this configuration is Single Point Positioning in Quick-Start mode from observations of a static receiver with precisely known position. The configuration uses GPS, GLONASS and Galileo observations and a Broadcast Ephemeris stream.


14. File 'SaveSp3.bnc'
    The purpose of this configuration is to produce SP3 files from a Broadcast Ephemeris stream and a Broadcast Corrections stream. The Broadcast Corrections stream is formally introduced in BNC's 'Combine Corrections' table. Note that producing SP3 requires an ANTEX file because SP3 file contents should be referred to CoM.


15. File 'Sp3ETRF2000PPP.bnc'
    The purpose of this configuration is to produce SP3 files from a Broadcast Ephemeris stream and a stream carrying ETRF2000 Broadcast Corrections. The Broadcast Corrections stream is formally introduced in BNC's 'Combine Corrections' table. This leads to an SP3 file containing orbits referred also to ETRF2000. Pulling in addition observations from a reference station at precisely known ETRF2000 position allows comparing an 'INTERNAL' PPP solution with ETRF2000 reference coordinates.


16. File 'Upload.bnc'
    The purpose of this configuration is to upload orbits and clocks from a real-time GNSS engine to an Ntrip Broadcaster. For that the configuration reads precise orbits and clocks in RTNET format. It also reads a stream carrying Broadcast Ephemeris. BNC converts the orbits and clocks into Broadcast Corrections and encodes them in RTCM Version 3 SSR messages to upload them to an Ntrip Broadcaster. The Broadcast Corrections stream is referred to satellite Antenna Phase Center (APC) and IGS08. Orbits are saved on disk in SP3 format and clocks in Clock RINEX format.


17. File 'UploadPPP.bnc'
    This configuration equals the 'Upload.bnc' configuration. However, the Broadcast Corrections are in addition used for an 'INTERNAL' PPP solution based on observations from a static reference station with known precise coordinates. This allows a continuous quality check of the Broadcast Corrections through observing coordinate displacements.


18. File 'Combi.bnc'
    The purpose of this configuration is to pull several streams carrying Broadcast Corrections and a Broadcast Ephemeris stream from an Ntrip Broadcaster to produce a combined Broadcast Corrections stream. BNC encodes the combination product in RTCM Version 3 SSR messages and uploads that to an Ntrip Broadcaster. The Broadcast Corrections stream is not referred to satellite Center of Mass (CoM). It is referred to IGS08. Orbits are saved in SP3 format and clocks in Clock RINEX format.


19. File 'CombiPPP.bnc'
    This configuration equals the 'Combi.bnc' configuration. However, the combined Broadcast Corrections are in addition used for an 'INTERNAL' PPP solutions based on observations from a static reference station with known precise coordinates. This allows a continuous quality check of the combination product through observing coordinate displacements.


20. File 'UploadEph.bnc'
    The purpose of this configuration is to pull a number of streams from reference stations to get hold of contained Broadcast Ephemeris messages. These are encoded then in a RTCM Version 3 stream which only provides Broadcast Ephemeris with an update rate of 5 seconds.


21. File 'CompareSp3.bnc'
    The purpose of this configuration is to compare two SP3 files to calculate RMS values for orbit and clock differences. GPS satellite G05 and GLONASS satellite R18 are excluded from this comparison. Comparison results are saved in a logfile.


22. File 'Empty.bnc'
    The purpose of this example is to provide an empty configuration file for BNC which only contains the default settings.

• In Qt-based desktop environments (like KDE) on Unix/Linux platforms it may happen that you experience a crash of BNC at startup even when running the program in the background using the '-nw' option. This is a known bug most likely resulting from an incompatibility of Qt libraries in the environment and in BNC. Entering the command 'unset SESSION_MANAGER' before running BNC may help as a work-around.
• Using RTCM Version 3 to produce RINEX files, BNC will properly handle most message types. However, when handling message types 1001, 1003, 1009 and 1011 where the ambiguity field is not set, the output will be no valid RINEX. All values will be stored modulo 299792.458 (speed of light).
• Using RTCM Version 2, BNC will only handle message types 18 and 19 or 20 and 21 together with position and the antenna offset information carried in types 3 and 22. Note that processing carrier phase corrections and pseudo-range corrections contained in message types 20 and 21 needs access to Broadcast Ephemeris. Hence, whenever dealing with message types 20 and 21, make sure that Broadcast Ephemeris become available for BNC through also retrieving at least one RTCM Version 3 stream carrying message types 1019 (GPS ephemeris) and 1020 (GLONASS ephemeris).
• BNC's 'Get Table' function only shows the STR records of a source-table. You can use an Internet browser to download the full source-table contents of any Ntrip Broadcaster by simply entering its URL in the form of http://host:port. Data field number 8 in the NET records may provide information about where to register for an Ntrip Broadcaster account.
• EUREF as well as IGS adhere to an open data policy. Streams are made available through Ntrip Broadcasters at www.euref-ip.net, www.igs-ip.net, products.igs-ip.net, and mgex.igs-ip.net free of charge to anyone for any purpose. There is no indication up until now how many users will need to be supported simultaneously. The given situation may develop in such a way that it might become difficult to serve all registered users at the same times. In cases where limited resources on the Ntrip Broadcaster side (software restrictions, bandwidth limitation etc.) dictates, first priority in stream provision will be given to stream providers followed by re-broadcasting activities and real-time analysis centers while access to others might be temporarily denied.
• Once BNC has been started, many of its configuration options cannot be changed as long as it is stopped. See chapter 'Reread Configuration' for on-the-fly configuration exceptions.
• Drag and drop of configuration files is currently not supported on Mac OS X. On such system you have to start BNC via command line.

The following chapters describes how to set the BNC program options. They explain the 'Top Menu Bar', the 'Settings Canvas' with the processing options, the contents of the 'Streams Canvas' and 'Logging Canvas', and the 'Bottom Menu Bar'.

The top menu bar allows selecting a font for the BNC windows, save configured options, or quit the program execution. It also provides access to the program's documentation.

The 'File' button lets you

• Select an appropriate font.
  Use smaller font size if the BNC main window exceeds the size of your screen.
• Reread and save selected options in configuration file.
  When using 'Reread & Save Configuration' while BNC is already processing data, some configuration options become immediately effective on-the-fly without interrupting uninvolved threads while all of them are saved on disk. See section 'Reread Configuration' for a list of on-the-fly changeable configuration options.
• Quit the BNC program.

The 'Help' button provides access to

• Help contents.
  You may keep the 'Help Contents' window open while configuring BNC.
• A 'Flow Chart' showing BNC linked to a real-time GNSS network engine such as RTNET.
• General information about BNC.
  Close the 'About BNC' window to continue working with BNC.

BNC comes with a What's This help system providing online information about its functionality and usage. Short descriptions are available for any widget and program option. Focus to the relevant object and press Shift+F1 to request help information. A help text appears immediately; it disappears as soon as the user does something else. The dialogs on some operating systems may provide a '?' button that users can click; click the relevant widget to pop up the help text.

You may need to specify a proxy when running BNC in a protected network. You may also like to use the Transport Layer Security (TLS) and its predecessor, Secure Sockets Layer (SSL) cryptographic protocols for secure Ntrip communication over the Internet.

If you are running BNC within a protected Local Area Network (LAN), you might need to use a proxy server to access the Internet. Enter your proxy server IP and port number in case one is operated in front of BNC. If you don't know the IP and port of your proxy server, check the proxy server settings in your Internet browser or ask your network administrator.

Note that IP streaming is often not allowed in a LAN. In this case you need to ask your network administrator for an appropriate modification of the local security policy or for the installation of a TCP relay to the Ntrip Broadcasters. If these are not possible, you might need to run BNC outside your LAN on a host that has unobstructed connection to the Internet.

Communication with an Ntrip Broadcaster over Secure Sockets Layer (SSL) as well as the download of RINEX skeleton files when available from HTTPS websites require the exchange of client and/or server certificates. Specify the path to a directory where you save certificates on your system. You may like to check out http://software.rtcm-ntrip.org/wiki/Certificates for a list of known Ntrip Server certificates. You may also just try communication via SSL to check out whether this is supported by the involved Ntrip Broadcaster.

SSL communication may involve queries coming from the Ntrip Broadcaster or from a HTTPS website hosting RINEX skeletons. Such a query could show up under BNC's 'Log' tab as follows:

   SSL Error
   Server Certificate Issued by:
   GNSS Data Center
   BKG (Bundesamt fuer Geodaesie und Kartographie)
   Cannot be verified

   The issuer certificate of a locally looked up certificate could not be found
   The root CA certificate is not trusted for this purpose
   No certificates could be verified

Figure 7: BNC's 'Network' panel configured to ignore eventually occurring SSL error messages.

The following defines general settings for BNC's logfile, file handling, reconfiguration on-the-fly, and auto-start.

Records of BNC's activities are shown in the 'Log' tab on the bottom of the main window. These logs can be saved into a file when a valid path is specified in the 'Logfile (full path)' field. The logfile name will automatically be extended by a string '_YYMMDD' carrying the current date. This leads to series of daily logfiles when running BNC continuously for extended. Message logs cover the communication status between BNC and the Ntrip Broadcaster as well as problems that may occur in the communication link, stream availability, stream delay, stream conversion etc. All times are given in UTC. The default value for 'Logfile (full path)' is an empty option field, meaning that BNC logs will not be saved into a file.

The following is an example for the contents of a logfile written by BNC when operated in Single Point Positioning (SPP) mode:

15-06-30 11:40:17 ========== Start BNC v2.12 (MAC) ==========
15-06-30 11:40:17 Panel 'PPP' active
15-06-30 11:40:17 CUT07: Get data in RTCM 3.x format
15-06-30 11:40:17 RTCM3EPH: Get data in RTCM 3.x format
15-06-30 11:40:17 Configuration read: PPP.conf, 2 stream(s)

15-06-30 11:40:21 2015-06-30_11:40:19.000 CUT07 X = -2364337.6814 Y = 4870283.8110 Z = -3360808.3085 NEU:  -0.0000  -0.0000  -0.0000 TRP:  +2.4026  -0.0001
15-06-30 11:40:22 2015-06-30_11:40:20.000 CUT07 X = -2364337.6853 Y = 4870283.8130 Z = -3360808.3082 NEU:  +1.1639  +0.6988  -2.1178 TRP:  +2.4018  +0.0003
15-06-30 11:40:23 2015-06-30_11:40:21.000 CUT07 X = -2364337.6862 Y = 4870283.8155 Z = -3360808.3107 NEU:  +0.1317  -0.4655  -4.4614 TRP:  +2.4009  +0.0009
15-06-30 11:40:24 2015-06-30_11:40:22.000 CUT07 X = -2364337.6864 Y = 4870283.8106 Z = -3360808.3099 NEU:  +0.1543  +0.2121  -1.0190 TRP:  +2.4022  +0.0009
15-06-30 11:40:25 2015-06-30_11:40:23.000 CUT07 X = -2364337.6861 Y = 4870283.8111 Z = -3360808.3105 NEU:  -0.9782  +0.0916  -2.3544 TRP:  +2.4017  +0.0013
15-06-30 11:40:26 2015-06-30_11:40:24.000 CUT07 X = -2364337.6884 Y = 4870283.8123 Z = -3360808.3103 NEU:  -0.5606  -0.0938  -1.9498 TRP:  +2.4018  +0.0016
15-06-30 11:40:27 2015-06-30_11:40:25.000 CUT07 X = -2364337.6913 Y = 4870283.8133 Z = -3360808.3122 NEU:  -0.1799  -0.1525  -4.8142 TRP:  +2.4007  +0.0025
15-06-30 11:40:28 2015-06-30_11:40:26.000 CUT07 X = -2364337.6919 Y = 4870283.8171 Z = -3360808.3184 NEU:  +0.7497  +0.7994  -2.0363 TRP:  +2.4018  +0.0032
15-06-30 11:40:29 2015-06-30_11:40:27.000 CUT07 X = -2364337.6923 Y = 4870283.8196 Z = -3360808.3230 NEU:  +0.8099  +0.5592  -2.8552 TRP:  +2.4015  +0.0039
15-06-30 11:40:30 2015-06-30_11:40:28.000 CUT07 X = -2364337.6960 Y = 4870283.8219 Z = -3360808.3222 NEU:  -0.2952  +1.9737  -4.5565 TRP:  +2.4008  +0.0047
15-06-30 11:40:31 2015-06-30_11:40:29.000 CUT07 X = -2364337.6982 Y = 4870283.8209 Z = -3360808.3209 NEU:  +0.3563  +2.1067  -5.5327 TRP:  +2.4005  +0.0057
...

When BNC is started, new files are created by default and any existing files with the same name will be overwritten. However, users might want to append existing files following a restart of BNC, a system crash or when BNC crashed. Tick 'Append files' to continue with existing files and keep what has been recorded so far. Note that option 'Append files' affects all types of files created by BNC.

When operating BNC online in 'no window' mode (command line option -nw), some configuration options can nevertheless be changed on-the-fly without interrupting the running process. For that you force the program to reread parts of its configuration in pre-defined intervals from the disk. Select '1 min', '1 hour', or '1 day' to let BNC reread on-the-fly changeable configuration options every full minute, hour, or day. This lets in between edited options become effective without interrupting uninvolved threads.

Note that the following configuration options saved on disk can be changed/edited on-the-fly while BNC is already processing data:

• 'mountPoints' to change the selection of streams to be processed, see section 'Streams';
• 'outWait' to change the 'Wait for full obs epoch' option, see section 'Feed Engine';
• 'outSampl' to change the 'Sampling' option, see section 'Feed Engine'.
• 'outFile' to change the 'File' name where synchronized observations are saved in plain ASCII format.

You may like to auto-start BNC at startup time in window mode with pre-assigned configuration options. This may be required i.e. immediately after booting your system. Tick 'Auto start' to supersede the usage of the 'Start' button. Make sure that you maintain a link to BNC for that in your Autostart directory (Windows systems) or call BNC in a script below directory /etc/init.d (Unix/Linux/Mac OS X systems).

See BNC's command line option '-nw' for an auto-start of BNC in 'no window' mode.

BNC can save all data coming in through various streams in one daily file. The information is recorded in the specified 'Raw output file' in the received order and format. This feature allows a BNC user to run the PPP option offline with observations, Broadcast Corrections, and Broadcast Ephemeris being read from a previously saved file. It supports the offline repetition of a real-time situation for debugging purposes and it is not meant for Post Processing.

Data will be saved in blocks in the received format separated by ASCII time stamps like (example):

   2010-08-03T18:05:28 RTCM3EPH RTCM_3 67

This example block header tells you that 67 bytes were saved in the data block following this time stamp. The information in this block is encoded in RTCM Version 3 format, comes from mountpoint RTCM3EPH and was received at 18:05:29 UTC on 2010-08-03. BNC adds its own time stamps in order to allow the reconstruction of a recorded real-time situation.

The default value for 'Raw output file' is an empty option field, meaning that BNC will not save all raw data into one single daily file.

Observations will be converted to RINEX if they come in either RTCM Version 2 or RTCM Version 3 format. Depending on the RINEX version and incoming RTCM message types, files generated by BNC may contain data from GPS, GLONASS, Galileo, SBAS, QZSS and/or BDS (BeiDou). In case an observation type is listed in the RINEX header but the corresponding observation is unavailable, its value is set to zero '0.000' or left blank. Note that the 'RINEX TYPE' field in the RINEX Version 3 Observation file header is always set to 'M(MIXED)' or 'Mixed' even if the file only contains data from one system.

It is important to understand that converting RTCM streams to RINEX files requires a priori information on observation types for specifying a complete RINEX header. Regarding the RINEX Version 2 file header, BNC simply introduces all observation types defined in the Version 2 standard and later reports "0.000" for all observations which are not received. However, following this approach is not possible for RINEX Version 3 files from RTCM Version 3 MSM streams because of the huge number of observation types which might in principle show up. The solution implemented in BNC is to start with RINEX Version 3 observation type records from skeleton files (see section 'Skeleton Extension' and 'Skeleton Mandatory') and switch to a default selection of observation types when such skeleton file is not available or does not contain the required information. The following is the default selection of observation types specified for a RINEX Version 3 file:

C    8 C1  C1P L1  S1  C2  C2P L2  S2                       SYS / # / OBS TYPES
E    8 C1  C1P L1  S1  C2  C2P L2  S2                       SYS / # / OBS TYPES
G    8 C1  C1W L1  S1  C2  C2W L2  S2                       SYS / # / OBS TYPES
J    8 C1  C1P L1  S1  C2  C2P L2  S2                       SYS / # / OBS TYPES
R    8 C1  C1P L1  S1  C2  C2P L2  S2                       SYS / # / OBS TYPES
S    8 C1  C1P L1  S1  C2  C2P L2  S2                       SYS / # / OBS TYPES

Please note that RTCM Version 3 messages 1084 for GLONASS observations don't contain the channel numbers. However, these messages can only be converted to RINEX when you add messages which include the channel numbers. This could be done though an additional stream carrying 1087 GLONASS observation messages or an additional stream carrying 1020 GLONASS ephemeris messages. You could also consider setting up a streams which contains both, the 1084 and the 1020 messages.

The screenshot below shows an example setup of BNC when converting streams to RINEX. Streams are coming from various Ntrip Broadcasters as well as from a serial communication link. Specifying a decoder string 'ZERO' means to not convert the affected stream but save its contents as received. The 'SSL Error' recorded in the 'Log' tab is caused by the fact that observation stream downloads from IGS and MGEX Broadcasters initiate the download of RINEX skeleton files from a HTTPS (TLS/SSL) website and BNC has been configured in this example to ignore SSL errors as shown in the preceding 'Network' panel screenshot.

Figure 8: BNC translating incoming observation streams to 15 min RINEX Version 3 Observation files.

The default for RINEX filenames in BNC follows the convention of RINEX Version 2. However, the software provides options to alternatively follow the filename convention of RINEX Version 3. RINEX Version 2 filenames are derived by BNC from the first 4 characters of the corresponding stream's mountpoint (4Char Station ID). For example, data from mountpoints FRANKFURT and WETTZELL will have hourly RINEX Observation files named

   FRAN{ddd}{h}.{yy}O
   WETT{ddd}{h}.{yy}O

where 'ddd' is the day of year, 'h' is a letter which corresponds to an hour long UTC time block and 'yy' is the year.

If there is more than one stream with identical 4Char Station ID (same first 4 characters for their mountpoints), the mountpoint strings are split into two sub-strings and both become part of the RINEX filename. For example, when simultaneously retrieving data from mountpoints FRANKFURT and FRANCE, their hourly RINEX Version 2 Observation files are named as

   FRAN{ddd}{h}_KFURT.{yy}O
   FRAN{ddd}{h}_CE.{yy}O

If several streams show exactly the same mountpoint name (example: BRUS0 from www.euref-ip.net and BRUS0 from www.igs-ip.net), BNC adds an integer number to the filename leading i.e. to hourly RINEX Version 2 Observation files like

   BRUS{ddd}{h}_0.{yy}O
   BRUS{ddd}{h}_1.{yy}O

Note that RINEX Version 2 filenames for all intervals less than 1 hour follow the filename convention for 15 minutes RINEX Version 2 Observation files i.e.

   FRAN{ddd}{h}{mm}.{yy}O

where 'mm' is the starting minute within the hour.

In case of RINEX Version 3 filenames, the following convention holds:

Parameter	# Char.	Meaning
Name	9	Site, station and country code
S	1	Data source
Start Time	11	YYYYDDDHHMM
Period	3	File period
Obs. Freq.	3	Observation frequency
Content	2	Content type
Format	3	File format
Compression	2-3	Compression method (optional)

Example for Mixed RINEX Version 3 GNSS observation filename, file containing 1 hour of data, one observation every second, 'MO' standing for 'Mixed Observations':

   ALGO00CAN_R_20121601000_01H_01S_MO.rnx

Note that filename details are produced from the streams mountpoint as well as corresponding BNC settings and meta data from the Ntrip Broadcaster source-table.

Here you can specify the path to where the RINEX Observation files will be stored. If the specified directory does not exist, BNC will not create RINEX Observation files. Default value for 'Directory' is an empty option field, meaning that no RINEX Observation files will be written.

Select the length of the RINEX Observation file generated. The default value is 15 minutes.

Select the RINEX Observation sampling interval in seconds. A value of zero '0' tells BNC to store all received epochs into RINEX. This is the default value.

Whenever BNC starts generating RINEX Observation files (and then once every day at midnight), it first tries to retrieve information needed for RINEX headers from so-called public RINEX header skeleton files which are derived from sitelogs. A HTTP or HTTPS link to a directory containing these skeleton files may be available through data field number 7 of the affected NET record in the source-table. See http://www.epncb.oma.be:80/stations/log/skl/brus.skl for an example of a public RINEX header skeleton file for EPN station Brussels. Note that the download of RINEX skeleton files from HTTPS websites requires the exchange of client and/or server certificates. Clarify 'SSL' options offered through panel 'Network' for details.

Sometimes public RINEX header skeleton files are not available, their contents is not up to date, or you need to put additional/optional records in the RINEX header. For that BNC allows using personal skeleton files that contain the header records you would like to include. You can derive a personal RINEX header skeleton file from the information given in an up to date sitelog. A file in the RINEX Observations 'Directory' with a 'Skeleton extension' suffix is interpreted by BNC as a personal RINEX header skeleton file for the corresponding stream.

When producing RINEX Observation files from mountpoints (examples) 'BRUS0', 'FRANKFURT'; and 'WETTZELL' the following skeleton filenames would be accepted

   BRUS.skl
   FRAN.skl
   WETT.skl

if 'Skeleton extension' is set to 'skl'.

Note the following regulations regarding personal RINEX header skeleton files:

• If such a file exists in the 'RINEX directory', the corresponding public RINEX header skeleton file is ignored. The RINEX header is generated solely from the contents of the personal skeleton.
• Personal skeletons should contain a complete first header record of type
  -   RINEX VERSION / TYPE
  
• They should then contain an empty header record of type
  -   PGM / RUN BY / DATE
  BNC will complete this line and include it in the RINEX file header.
• They should further contain complete header records of type
  -   MARKER NAME
  -   OBSERVER / AGENCY
  -   REC # / TYPE / VERS
  -   ANT # / TYPE
  -   APPROX POSITION XYZ
  -   ANTENNA: DELTA H/E/N
  -   WAVELENGTH FACT L1/2 (RINEX Version 2)

-   SYS / # / OBS TYPES (for RINEX Version 3 files, will be ignored when writing Version 2 files)
• They may contain any other optional complete header record as defined in the RINEX documentation.
• They should also contain an empty header records of type
  -   # / TYPES OF OBSERV (only RINEX Version 2, will be ignored when writing RINEX Version 3 files)
  BNC will include these lines in the final RINEX file header together with an additional
  -   COMMENT
  line describing the source of the stream.
• They should finally contain an empty header record of type
  -   END OF HEADER (last record)
• They must not contain a header record of type
  -   TIME OF FIRST OBS

If neither a public nor a personal RINEX header skeleton file is available for BNC, a default header will be used.

The following is a skeleton example for a RINEX file:

	            OBSERVATION DATA    M (MIXED)           RINEX VERSION / TYPE
CUT0                                                        MARKER NAME         
59945M001                                                   MARKER NUMBER       
5023K67889          TRIMBLE NETR9       5.01                REC # / TYPE / VERS 
4928353386          TRM59800.00     SCIS                    ANT # / TYPE        
 -2364337.2699  4870285.5624 -3360809.8398                  APPROX POSITION XYZ 
        0.0000        0.0000        0.0000                  ANTENNA: DELTA H/E/N
gnss@curtin.edu.au  CUT                                     OBSERVER / AGENCY   
C   10 C1I L1I D1I S1I C6I L6I S6I C7I L7I S7I              SYS / # / OBS TYPES
E   13 C1X L1X D1X S1X C5X L5X S5X C7X L7X S7X C8X L8X S8X  SYS / # / OBS TYPES
G   13 C1C L1C D1C S1C C2W L2W S2W C2X L2X S2X C5X L5X S5X  SYS / # / OBS TYPES
J   19 C1C L1C D1C S1C C1X L1X S1X C1Z L1Z S1Z C2X L2X S2X  SYS / # / OBS TYPES
       C5X L5X S5X C6L L6L S6L                              SYS / # / OBS TYPES
R   13 C1C L1C D1C S1C C1P L1P S1P C2C L2C S2C C2P L2P S2P  SYS / # / OBS TYPES
S    7 C1C L1C D1C S1C C5I L5I S5I                          SYS / # / OBS TYPES
PORTIONS OF THIS HEADER GENERATED BY THE IGS CB FROM        COMMENT             
SITELOG cut0_20150507.log                                   COMMENT             
                                                            END OF HEADER

Tick check box 'Skeleton mandatory' in case you want that RINEX files are only produced if skeleton files are available for BNC. If no skeleton file is available for a particular source then no RINEX observation file will be produced from the affected stream.

Note that a skeleton file contains RINEX header information such as receiver and antenna types. In case of stream conversion to RINEX Version 3 a skeleton file should also contain information on potentially available observation types. A missing skeleton file will therefore enforce BNC to only save a default set of RINEX 3 observation types.

Whenever a RINEX Observation file is saved, you might want to compress, copy or upload it immediately via FTP. BNC allows you to execute a script/batch file to carry out these operations. To do that, specify the full path of the script/batch file here. BNC will pass the RINEX Observation file path to the script as a command line parameter (%1 on Windows systems, $1 on Unix/Linux/Mac OS X systems).

The triggering event for calling the script or batch file is the end of a RINEX Observation file 'Interval'. If that is overridden by a stream outage, the triggering event is the stream reconnection.

As an alternative to initiating file uploads through BNC, you may like to call an upload script or batch file through your crontable or Task Scheduler (independent from BNC) once every one or two minutes after the end of each RINEX file 'Interval'.

GNSS observation data are generally hold available within BNC according to attributes as defined in RINEX Version 3. These attributes describe the tracking mode or channel when generating the observation signals. Capital letters specifying signal generation attributes are A, B, C, D, I, L, M, N, P, Q, S, W, X, Y, and Z, see RINEX Version 3 documentation. Although RINEX Version 3 with its signal generation attributes is the internal default processing format for BNC, there are two applications where the program is explicitly required to produce data in RINEX Version 2 format:

1. When saving the contents of incoming observation streams in RINEX Version 2 files as described in this section.
2. When editing or concatenating RINEX 3 files to save them in Version 2 format, see section on 'RINEX Editing & QC'.

The default 'Signal priority' list is an empty option string meaning a priority sequence of 'CWPX_?' attributes when mapping RINEX 3 to RINEX 2. The meaning of this sequence of characters - take it as an example - is as follows:

• Signals with attribute 'C' enjoy the highest priority. If such a Version 3 observation becomes available it is presented as RINEX Version 2 observation if that is the format you wish to see. Observations with other attributes are ignored.
• If no signal with 'C' attribute is available but we have an observation with 'W' attribute, BNC presents that one as RINEX Version 2 observation and ignores all observations with other attributes. The same applies mutatis mutandis to observations with P and X attributes.
• If no signal with 'C', 'W', 'P', or 'X' attribute is available but a signal with undefined generation attribute (underscore character, '_') exists, BNC presents that one as RINEX Version 2 observation. Note that observation attributes should actually always be available in RINEX Version 3. Hence the underscore character makes only sense in a few very special cases.
• If no signal with 'C', 'W', 'P', 'X', or '_' generation attribute exists then the question mark '?' tells BNC to present the first of any other appearing signal as RINEX Version 2 observation.

Signal priorities can be specified either as equal for all systems or system specific. The following are example priority strings:

• CWPX_? (Same signal priorities valid for all systems)
• G:CWPX_? R:PCX_? E:CPX_? (Specific signal priorities for GPS, GLONASS and Galileo system)

You may like to specify you own 'Signal priority' string(s) for producing RINEX Version 2 files. If you neither convert observation streams to RINEX Version 2 nor concatenate RINEX Version 3 to Version 2 files then the 'Version 2' option is meaningless.

The default format for RINEX Observation files is RINEX Version 2.11. Select RINEX 'Version 3' if you would like to save RTCM Version 3 observation streams in RINEX Version 3 format.

Note that it is possible to force a RTCM Version 2 stream to be saved in RINEX Version 3 file format. However, this is not recommended because such stream cannot be precisely mapped to RINEX Version 3 as the required information on tracking modes (observation attributes) is not part of RTCM Version 2.

Tick check box 'Version 3 filenames' to let BNC create so-called extended filenames following the RINEX Version 3 standard.

Default is an empty check box, meaning to still use filenames following the RINEX Version 2 standard although the file contents is saved in RINEX Version 3 format.

Broadcast Ephemeris can be saved as RINEX Navigation files when received via RTCM Version 3 e.g. as message types 1019 (GPS) or 1020 (GLONASS) or 1044 (QZSS) or 1043 (SBAS) or 1045 and 1046 (Galileo) or 63 (tentative, BDS/BeiDou). The filename convention follows the details given in section 'RINEX Filenames' except that the first four characters are 'BRDC'.

For RINEX Version 2 Navigation files the last character is 'N' or 'G' for GPS or GLONASS ephemeris in two separate files.

Regarding RINEX Version 3 you will find all ephemeris data for GPS, GLONASS, Galileo, SBAS, QZSS, and BDS saved together in one Navigation file.

The following is an example for a RINEX Version 3 Navigation filename. The file contains one days data. 'MN' stands for 'Multi Constellation Navigation' data.

   BRDC00DEU_S_20121600000_01D_MN.rnx

Note that streams dedicated to carry Broadcast Ephemeris messages in RTCM Version 3 format in high repetition rates are listed on http://igs.bkg.bund.de/ntrip/ephemeris.

Note further that BNC will ignore incorrect or outdated Broadcast Ephemeris data when necessary, leaving a note 'WRONG EPHEMERIS' or 'OUTDATED EPHEMERIS' in the logfile.

Specify a path for saving Broadcast Ephemeris data as RINEX Navigation files. If the specified directory does not exist, BNC will not create RINEX Navigation files. Default value for Ephemeris 'Directory' is an empty option field, meaning that no RINEX Navigation files will be created.

Select the length of RINEX Navigation files. The default value is '1 day'.

BNC can output Broadcast Ephemeris in RINEX Version 3 format on your local host (IP 127.0.0.1) through an IP 'Port'. Specify an IP port number to activate this function. The default is an empty option field, meaning that no ASCII ephemeris output via IP port is generated.

The source code for BNC comes with an example Perl script 'test_tcpip_client.pl' that allows you to read BNC's ASCII ephemeris output from the IP port.

Default format for RINEX Navigation files containing Broadcast Ephemeris is RINEX Version 2.11. Select 'Version 3' if you want to save the ephemeris data in RINEX Version 3 format.

Note that this does not concern the Broadcast Ephemeris output through IP port which is always in RINEX Version 3 format.

Tick check box 'Version 3 filenames' to let BNC create so-called extended filenames following the RINEX Version 3 standard.

Default is an empty check box, meaning to still use filenames following the RINEX Version 2 standard although the file contents is saved in RINEX Version 3 format.

Figure 9: Converting Broadcast Ephemeris stream to RINEX Version 3 Navigation file.

Besides stream conversion from RTCM to RINEX, BNC allows editing RINEX files or concatenate their contents. RINEX Observation and Navigation files can be handled. BNC can also carry out a RINEX file Quality Check. In summary and besides Stream Translation this functionality in BNC covers

• File Editing and concatenation
• File Quality Check
• Multipath analysis sky plots
• Signal-to-noise ratio sky plots
• Satellite availability plots
• Satellite elevation plots
• PDOP plots

Select an action. Options are 'Edit/Concatenate' and 'Analyze'.

• Select 'Edit/Concatenate' if you want to edit RINEX file contents according to options specified under 'Set Edit Options' or if you want to concatenate several RINEX files.
• Select 'Analyze' if you are interested in a quality check of your RINEX file contents.

Specify full path to input RINEX Observation file(s), and
specify full path to input RINEX Navigation file(s).

When specifying several input files BNC will concatenate their contents. In case of RINEX Observation input files with different observation type header records, BNC will output only one specific set of adjusted observation type records in the RINEX header which fits to the whole file contents.

Note that you may specify several RINEX Version 2 Navigation files for GPS and GLONASS.

If 'Edit/Concatenate' is selected, specifying the full path to output RINEX Observation file(s) and specifying the full path to output RINEX Navigation file(s) is optional. Default are empty option fields, meaning that no RINEX files will be saved on disk.

Specify the name of a logfile to save information on RINEX file Editing/Concatenation or Analysis. Default is an empty option field, meaning that no logfile will be saved.

Note that logfiles from analyzing RINEX files may become quite large. Hence BNC provides an option 'Summary only' to limit this logfile contents to some essential information in case 'Action' is set to 'Analyze'. The following is an example for a RINEX quality check analysis logfile:

QC Format Version : 1.0

Navigation File(s): brdm1660.15p
Ephemeris         : 6421 OK   4 BAD
Bad Ephemeris   : brdm1660.15p S27 2015 06 15 05 04 00 
Bad Ephemeris   : brdm1660.15p S27 2015 06 15 05 46 40 
Bad Ephemeris   : brdm1660.15p S27 2015 06 15 05 59 28 
Bad Ephemeris   : brdm1660.15p C08 2015 06 15 08 00 00-

Observation File  : cut01660.15o
RINEX Version     : 3.02
Marker Name       : CUT0
Marker Number     : 59945M001
Receiver          : TRIMBLE NETR9
Antenna           : TRM59800.00     SCIS
Position XYZ      :  -2364337.2971   4870285.5843  -3360809.8188
Antenna dH/dE/dN  :   0.0000   0.0000   0.0000
Start Time        : 2015-06-15 00.00.00.0
End Time          : 2015-06-15 23.59.30.0
Interval          : 30
Navigation Systems: 6    C E G J R S

C: Satellites: 13
C: Signals   : 3    2I 6I 7I

C:   2I: Observations      :  29094
C:   2I: Slips (file+found):    183 +     2
C:   2I: Gaps              :     31
C:   2I: Mean SNR          :   42.2
C:   2I: Mean Multipath    :   0.40

C:   6I: Observations      :  29048
C:   6I: Slips (file+found):    191 +     0
C:   6I: Gaps              :     57
C:   6I: Mean SNR          :   44.8
C:   6I: Mean Multipath    :   0.00

C:   7I: Observations      :  29048
C:   7I: Slips (file+found):    191 +     2
C:   7I: Gaps              :     57
C:   7I: Mean SNR          :   44.4
C:   7I: Mean Multipath    :   0.30

E: Satellites: 7
E: Signals   : 4    1X 5X 7X 8X

E:   1X: Observations      :   7440
E:   1X: Slips (file+found):    332 +     1
E:   1X: Gaps              :     11
E:   1X: Mean SNR          :   44.3
E:   1X: Mean Multipath    :   0.36
...

G: Satellites: 31
G: Signals   : 4    1C 2W 2X 5X

G:   1C: Observations      :  31331
G:   1C: Slips (file+found):    959 +    20
G:   1C: Gaps              :     81
G:   1C: Mean SNR          :   44.2
G:   1C: Mean Multipath    :   0.69
...

J: Satellites: 1
J: Signals   : 6    1C 1X 1Z 2X 5X 6X

J:   1C: Observations      :   2880
J:   1C: Slips (file+found):     43 +     0
J:   1C: Gaps              :      0
J:   1C: Mean SNR          :   44.0
J:   1C: Mean Multipath    :   0.60
...

R: Satellites: 24
R: Signals   : 4    1C 1P 2C 2P

R:   1C: Observations      :  24500
R:   1C: Slips (file+found):    194 +    36
R:   1C: Gaps              :     76
R:   1C: Mean SNR          :   45.2
R:   1C: Mean Multipath    :   0.81
...

S: Satellites: 4
S: Signals   : 2    1C 5I

S:   1C: Observations      :  11520
S:   1C: Slips (file+found):      5 +   145
S:   1C: Gaps              :      0
S:   1C: Mean SNR          :   41.1
S:   1C: Mean Multipath    :   0.91
...

> 2015 06 15 00 00  0.0000000 39  0.6
G14   1.50   14.90   2  L1C s. 32.4  C1C  . 0.76
G15  11.79  117.66   6  L1C .. 39.1  C1C  . 0.86  L2W .. 20.9  C2W  . 1.10  L2X .. 37.1  C2X  . 1.11
G16  53.56 -107.67   4  L1C .. 48.8  C1C  . 0.31  L2W .. 39.9  C2W  . 0.26
G18  72.61   84.24   4  L1C .. 50.0  C1C  . 0.29  L2W .. 43.1  C2W  . 0.26
G19   6.07 -124.61   4  L1C .. 36.1  C1C  . 0.91  L2W .. 18.6  C2W  . 0.43
G20   4.75  138.88   4  L1C s. 35.5  C1C  . 0.00  L2W s. 15.6  C2W  . 0.00
G21  40.44  132.24   4  L1C .. 45.7  C1C  . 0.59  L2W .. 33.3  C2W  . 0.24
G22  55.62  -12.81   4  L1C .. 51.6  C1C  . 0.44  L2W .. 41.7  C2W  . 0.26
G26  56.96  -45.95   8  L1C .. 50.8  C1C  . 0.56  L2W .. 42.7  C2W  . 0.23  L2X .. 50.7  C2X  . 0.30  L5X .. 55.7  C5X  . 0.00
G27  33.71 -136.99   8  L1C .. 46.9  C1C  . 0.51  L2W .. 35.5  C2W  . 0.34  L2X .. 45.9  C2X  . 0.36  L5X .. 52.0  C5X  . 0.00
G29  15.74   68.66   6  L1C .. 41.3  C1C  . 0.93  L2W .. 22.8  C2W  . 0.44  L2X .. 38.1  C2X  . 0.37
R01  52.20  117.58   8  L1C .. 52.5  C1C  . 0.42  L1P .. 50.5  C1P  . 0.39  L2C .. 43.8  C2C  . 0.49  L2P .. 43.5  C2P  . 0.39
R02  47.13   19.13   8  L1C .. 53.3  C1C  . 0.31  L1P .. 52.0  C1P  . 0.45  L2C .. 47.9  C2C  . 0.39  L2P .. 47.6  C2P  . 0.39
R03   3.03  -10.43   8  L1C .. 36.0  C1C  . 2.06  L1P .. 34.4  C1P  . 1.03  L2C .. 36.6  C2C  . 0.69  L2P .. 37.0  C2P  . 0.65
R08   9.52  152.59   8  L1C .. 41.3  C1C  . 1.11  L1P .. 39.9  C1P  . 0.76  L2C .. 38.3  C2C  . 0.89  L2P .. 38.1  C2P  . 0.63
R14  15.31  -50.83   8  L1C .. 39.0  C1C  . 1.16  L1P .. 37.4  C1P  . 0.78  L2C .. 34.3  C2C  . 0.63  L2P .. 34.0  C2P  . 0.57
R15  22.97  -99.16   8  L1C .. 43.7  C1C  . 0.72  L1P .. 42.2  C1P  . 0.47  L2C .. 42.0  C2C  . 0.46  L2P .. 42.2  C2P  . 0.39
R16   4.62 -152.37   8  L1C .. 40.4  C1C  . 1.24  L1P .. 39.1  C1P  . 0.89  L2C .. 35.3  C2C  . 0.73  L2P .. 33.9  C2P  . 0.57
R17  42.68 -161.68   8  L1C .. 50.6  C1C  . 0.56  L1P .. 48.6  C1P  . 0.43  L2C .. 39.1  C2C  . 0.56  L2P .. 38.4  C2P  . 0.32
R23  14.50   88.21   8  L1C .. 43.8  C1C  . 1.25  L1P .. 42.5  C1P  . 0.61  L2C .. 35.2  C2C  . 0.88  L2P .. 34.3  C2P  . 0.59
R24  47.18  133.41   8  L1C .. 47.0  C1C  . 0.48  L1P .. 46.0  C1P  . 0.45  L2C .. 42.9  C2C  . 0.40  L2P .. 43.1  C2P  . 0.32
E18   0.00    0.00   8  L1X .. 45.0  C1X  . 0.58  L5X .. 47.2  C5X  . 0.26  L7X .. 46.1  C7X  . 0.00  L8X .. 51.1  C8X  . 0.00
J01  79.88   57.76  12  L1C .. 49.9  C1C  . 0.18  L1X .. 53.8  C1X  . 0.25  L1Z .. 51.3  C1Z  . 0.26  L2X .. 51.3  C2X  . 0.23  L5X .. 55.9  C5X  . 0.00  L6X .. 46.5  C6X  . 0.00
S27  16.07  -73.59   4  L1C .. 36.8  C1C  . 0.92  L5I .. 41.7  C5I  . 0.75
S28  38.67  -50.73   4  L1C s. 44.9  C1C  . 0.00  L5I s. 45.0  C5I  . 0.00
S29  41.34   46.37   2  L1C .. 39.2  C1C  . 0.00
S37  41.34   46.37   2  L1C .. 39.9  C1C  . 0.00
C01 -14.73  163.85   6  L2I .. 42.5  C2I  . 0.47  L7I .. 46.6  C7I  . 0.23  L6I .. 45.5  C6I  . 0.00
C02  33.21  145.93   6  L2I .. 37.9  C2I  . 0.29  L7I .. 43.0  C7I  . 0.18  L6I .. 43.3  C6I  . 0.00
C03 -37.46  -58.16   6  L2I .. 44.1  C2I  . 0.21  L7I .. 46.6  C7I  . 0.21  L6I .. 47.3  C6I  . 0.00
C04  64.99   -5.73   6  L2I .. 37.7  C2I  . 0.37  L7I .. 41.8  C7I  . 0.25  L6I .. 42.9  C6I  . 0.00
C05 -42.36  -80.31   6  L2I .. 35.9  C2I  . 0.27  L7I .. 38.7  C7I  . 0.21  L6I .. 39.6  C6I  . 0.00
C06 -15.26  -74.59   6  L2I .. 47.0  C2I  . 0.60  L7I .. 47.1  C7I  . 0.24  L6I .. 48.0  C6I  . 0.00
C07  34.21   14.11   6  L2I .. 32.8  C2I  . 0.87  L7I .. 36.4  C7I  . 0.40  L6I .. 35.2  C6I  . 0.00
C08  -0.07 -107.77   6  L2I .. 49.7  C2I  . 0.17  L7I .. 49.1  C7I  . 0.21  L6I .. 50.2  C6I  . 0.00
C09 -10.42  107.30   6  L2I .. 41.6  C2I  . 0.54  L7I .. 42.6  C7I  . 0.37  L6I .. 42.3  C6I  . 0.00
C10  32.77    7.17   6  L2I .. 36.9  C2I  . 0.87  L7I .. 36.7  C7I  . 0.58  L6I .. 36.0  C6I  . 0.00
C11  33.14   61.19   6  L2I .. 43.1  C2I  . 0.57  L7I .. 44.0  C7I  . 0.52  L6I .. 43.6  C6I  . 0.00
C14 -22.42  106.32   6  L2I .. 49.6  C2I  . 0.35  L7I .. 50.7  C7I  . 0.26  L6I .. 52.3  C6I  . 0.00
> 2015 06 15 00 00 30.0000000 39  0.6
...

Note that in addition to cycle slips recorded in the RINEX 'file', cycle slips identified by BNC are reported as 'found'.

Multipath and signal-to-noise sky plots as well as plots for satellite availability, elevation and PDOP are produced per GNSS system and frequency with the multipath analysis based on CnC observation types (n = band / frequency). The 'Plots for signals' option lets you exactly specify the observation signals to be used for that and also enables the plot production. You can specify the navigation system (C = BDS, E = Galileo, G = GPS, J = QZSS, R = GLONASS, S = SBAS), the frequency, and the tracking mode or channel as defined in RINEX Version 3. Specifications for frequency and tracking mode or channel must be separated by ampersand character '&'. Specifications for each navigation systems must be separated by blank character ' '. The following string is an example for option field 'Plots of signals': It lets you exactly specify the observation signals to be used and also enables the plot generation. You can specify the navigation system, the frequency, and the tracking mode or channel as defined in RINEX Version 3. Specifications for frequency and tracking mode or channel must be separated by ampersand character '&'. Specifications for each navigation systems must be separated by blank character ' '.

C:2&7 E:1&5 G:1&2 J:1&2 R:1&2 S:1&5

• BDS plots for L2 and L7,
• Galileo plots for L1 and L5,
• GPS plots for L1 and L2,
• QZSS plots for L1 and L2,
• GLONASS plots for L1 and L2,
• SBAS plots for L1 and L5.

If 'Analyze' is selected, specifying the path to a directory where plot files will be saved is optional. Filenames will be composed from the RINEX input filename(s) plus suffix 'PNG' to indicate the plot file format in use. Default is an empty option field, meaning that plots will not be saved on disk.

Once the 'Edit/Concatenate' action is selected, you have to 'Set Edit Options'. BNC lets you specify the RINEX version, a signal priority list when mapping RINEX Version 3 to Version 2, the sampling interval, begin and end of file, operator, observation types, comment lines, and marker, antenna, receiver details. Note that some of the specifications for editing and concatenation are only meaningful for RINEX Observation files but not for RINEX Navigation files.

A note on converting RINEX Version 3 to RINEX Version 2 and vice versa:

• The RINEX Version 2 format ignores signal generation attributes. Therefore, when converting RINEX Version 3 to Version 2 Observation files, BNC is forced to somehow map signals with attributes to signals without attributes although this can't be done in one-to-one correspondence. Hence we introduce a 'Version 2 Signal Priority' list of attributes (characters, forming a string) for mapping Version 3 to Version 2, see details in section 'RINEX Observations/Version 2'. The default 'Version 2 Signal Priority' list of observation attributes when mapping RINEX Version 3 to Version 2 is 'CWPX_?'. Signal priorities can be specified either as equal for all systems or system specifics. The following are example priority strings:
• CWPX_? (Same signal priorities valid for all systems)
• G:CWPX_? R:PCX_? E:CPX_? (Specific signal priorities for GPS, GLONASS and Galileo system)


• When converting RINEX Version 2 to Version 3 Observation files, the tracking mode or channel information in the (last character out of the three characters) observation code is left blank if unknown. This is a compromise, knowing that it is not in accordance with the RINEX Version 3 documentation.

Optionally you may specify a 'RUN BY' string to be included in the emerging new RINEX file header. Default is an empty option field, meaning the operator's ID is automatically used as 'RUN BY' string.

You can specify a list of observation codes in field 'Use Obs. Types' to limit the output file contents to specific observation codes. GNSS system characters in that list are followed by a colon and a two or three characters observation code. A two characters observation code would mean that all available tracking modes of the affected observation type and frequency will be accepted as part of the RINEX output file. Observation codes are separated by a blank character. Default is an empty option field, meaning that any input observation code will become part of the RINEX output file.

Specifying comment line text to be added to the emerging new RINEX file header is another option. Any introduction of a newline through '\n' in this enforces the beginning of a further comment line. Comment line(s) will be added to the header immediately after the 'PGM / RUN BY / DATE' record. Default is an empty option field, meaning that no additional comment line will be added to the RINEX header.

If you specify a 'New' but no 'Old' marker/antenna/receiver name, the corresponding data field in the emerging new RINEX Observation file will be filled accordingly. If you in addition specify an 'Old' marker/antenna/receiver name, the corresponding data field in the emerging new RINEX Observation file will only be filled accordingly where 'Old' specifications match existing file contents.

Figure 10: Example for 'RINEX Editing Options' window.

Figure 11: Example for RINEX file concatenation with BNC.

Figure 12: Example for creating RINEX quality check analysis graphics output with BNC.

Figure 13: Example for satellite availability, elevation and PDOP plots as a result of a RINEX quality check analysis with BNC.

Figure 14: Sky plot examples for multipath, part of RINEX quality check analysis with BNC.

Figure 15: Sky plot examples for signal-to-noise ratio, part of RINEX quality check analysis with BNC.

BNC applies options from the configuration file but allows updating every one of them on the command line while the contents of the configuration file remains unchanged, see section on 'Command Line Options'. The syntax for that looks as follows

   --key <keyName> <keyValue>

where <keyName> stands for the name of an option contained in the configuration file and <keyValue> stands for the value you want to assign to it. This functionality may be helpful in the 'RINEX Editing & QC' context when running BNC on a routine basis for maintaining a RINEX file archive.

   ./bnc --nw --conf rnx.conf --key reqcAction Edit/Concatenate --key reqcObsFile "tlse119b00.12o,tlse119b15.12o,tlse119b30.12o,tlse119b45.12o" --key reqcOutObsFile tlse119b.12o --key reqcRnxVersion 3 --key reqcSampling 30

You may use asterisk '*' and/or question mark '?' wildcard characters as shown with the following globbing command line option to specify a selection of files in a local directory:

   --key reqcObsFile "tlse*"
or:
   --key reqcObsFile tlse\*

The following Linux command line produces RINEX QC plots (see Estey and Meertens 1999) offline in 'no window' mode and saves them in directory '/home/user'. Introducing a dummy configuration file /dev/null makes sure that no configuration options previously saved on disc are used:

   /home/user/bnc --conf /dev/null --key reqcAction Analyze --key reqcObsFile CUT02070.12O --key reqcNavFile BRDC2070.12P --key reqcOutLogFile CUT0.txt --key reqcPlotDir /home/user --nw

The following Linux command line produces the same RINEX QC plots in interactive autoStart mode:

   /home/user/bnc --conf /dev/null --key reqcAction Analyze --key reqcObsFile CUT02070.12O --key reqcNavFile BRDC2070.12P --key reqcOutLogFile CUT0.txt --key --key startTab 4 --key autoStart 2

The following is a list of available key names for 'RINEX Editing & QC' (short: REQC, pronounced 'rek') options and their meaning, cf. section 'Configuration Examples':

BNC allows to compare the contents of two files containing GNSS orbit and clock data in SP3 format. SP3 ASCII files basically contain a list of records over a certain period of time. Each record carries a time tag, the XYZ position of the satellite's Center of Mass at that time and the corresponding satellite clock value. Both SP3 files may contain some records for different epochs. If so then BNC only compares records for identical epochs. BNC accepts that a specific GNSS system or a specific satellite is only available from one of the SP3 files. Note that BNC does not interpolate orbits when comparing SP3 files.

To compare satellite clocks provided by the two files BNC first converts coordinate differences dX,dY,dZ into along track, out-of-plane and radial components. It then corrects the clock differences for the radial components of coordinate differences. RMS values of clock differences are finally calculated after introducing at first one offset 'per epoch for all satellites' and secondly one offset 'per satellite for all epochs'.

Specify the full path of two SP3 files separated by a comma.

You may want to exclude one or more satellites in your SP3 files from the comparison. Or you may like to exclude all satellites of a specific GNSS system from the comparison. The following are example strings to be entered for excluding satellites from the comparison.

• G05,G31 (excluding GPS satellites with PRN 5 and 31)
• G (excluding all GPS satellites)
• R (excluding all GLONASS satellites)
• R12,R24 (excluding GLONASS satellites with slot number 12 and 24)
• G04,G31,R (excluding GPS satellites with PRN 4 and 31 as well as all GLONASS satellites)

Default is an empty option field, meaning that no satellite will be excluded from the comparison.

Specify a logfile name to save results of the SP3 file comparison.

The following is an example for a SP3 Comparison logfile:

! SP3 File 1: esr18283.sp3
! SP3 File 2: rt218283.sp3
!
!  MJD       PRN  radial   along   out        clk    clkRed   iPRN
! ----------------------------------------------------------------
57043.000000 G01 -0.0001 -0.0318 -0.0354     0.0266  0.0267     1
57043.000000 G02 -0.0062 -0.0198  0.0111     0.0082  0.0143     2
57043.000000 G03  0.0052  0.0060  0.0032     0.0386  0.0334     3
57043.000000 G04 -0.0049 -0.0193 -0.0071    -0.1696 -0.1648     4
57043.000000 G05  0.0027  0.0154  0.0275     0.0345  0.0318     5
57043.000000 G06  0.0247 -0.0398 -0.0111     0.0483  0.0236     6
57043.000000 G07 -0.0052  0.2854 -0.0975    -0.0940 -0.0888     7
57043.000000 G08 -0.0247  0.0937 -0.0184    -0.1563 -0.1316     8
57043.000000 G09  0.0152  0.0583  0.0086    -0.0144 -0.0296     9
...
...
...
!
! RMS[m]
!
!   PRN  radial   along   out     nOrb    clk   clkRed   nClk    Offset
! ---------------------------------------------------------------------
!   G01  0.0151  0.0377  0.0196     96  0.0157  0.0154     96    0.0152
!   G02  0.0083  0.0278  0.0228     96  0.0097  0.0124     96   -0.0626
!   G03  0.0105  0.0311  0.0307     96  0.0352  0.0309     96    0.0898
!   G04  0.0113  0.0334  0.0154     94  0.0725  0.0707     94   -0.5087
!   G05  0.0103  0.0319  0.0299     96  0.0417  0.0403     96    0.1185
!   G06  0.0182  0.0509  0.0302     96  0.0218  0.0166     96    0.0040
!   G07  0.0337  0.1632  0.0463     96  0.0483  0.0435     96    0.3031
!   G08  0.0228  0.0741  0.0321     88  0.0616  0.0561     88   -0.2232
...
...
...
!   R20  0.0637  0.2115  0.1131     96  0.1580  0.1345     96    0.7371
!   R21  0.0475  0.1657  0.0880     96  0.1123  0.0840     96   -0.4133
!   R22  0.0125  0.1249  0.0646     96  0.0414  0.0444     96   -0.7375
!   R23  0.0435  0.1503  0.0573     96  0.0987  0.1099     96    0.6620
!   R24  0.0278  0.2026  0.1186     96  0.1446  0.1303     96   -1.1470
!
! Total  0.0262  0.0938  0.0492   5268  0.0620  0.0561   5268

The first part in this uses the following abbreviations:

The second part following string 'RMS' provides a summary of the comparison using the following abbreviations:

Figure 16: BNC configuration example for comparing two SP3 files with satellite orbit and clock data.

Differential GNSS and RTK operation using RTCM streams is currently based on corrections and/or raw measurements from single or multiple reference stations. This approach to differential positioning is using 'observation space' information. The representation with the RTCM standard can be called 'Observation Space Representation' (OSR).

An alternative to the observation space approach is the so called 'sate space' approach. The principle here is to provide information on individual error sources. It can be called 'State Space Representation' (SSR). For a rover position, state space information concerning precise satellite clocks, orbits, ionosphere, troposphere et cetera can be converted into observation space and used to correct the rover observables for more accurate positioning. Alternatively the state information can directly be used in the rover's processing or adjustment model.

RTCM is currently developing Version 3 messages to transport SSR corrections in real-time. They refer to satellite Antenna Phase Center (APC). SSR messages adopted or recently proposed concern:

• SSR, Step I:
• Orbit corrections to Broadcast Ephemeris
• Clock corrections to Broadcast Ephemeris
• High-rate clock corrections to Broadcast Ephemeris
• Combined orbit and clock corrections to Broadcast Ephemeris
• User Range Accuracy (URA)
• High Rate User Range Accuracy (HR URA)
• Code biases
• SSR, Step II:
• Phase biases
• Vertical Total Electron Content (VTEC)

RTCM Version 3 streams carrying these messages may be used i.e. to support real-time Precise Point Positioning (PPP) applications.

When using clocks from Broadcast Ephemeris (with or without applied corrections) or clocks from SP3 files, it may be important to understand that they are not corrected for the conventional periodic relativistic effect. Chapter 10 of the IERS Conventions 2003 mentions that the conventional periodic relativistic correction to the satellite clock (to be added to the broadcast clock) is computed as dt = -2 (R * V) / c^2 where R * V is the scalar product of the satellite position and velocity and c is the speed of light. This can also be found in the GPS Interface Specification, IS-GPS-200, Revision D, 7 March 2006.

Orbit corrections are provided in along-track, cross-track and radial components. These components are defined in the Earth-centered, Earth-fixed reference frame of the broadcast ephemerides. For an observer in this frame, the along-track component is aligned in both direction and sign with the velocity vector, the cross-track component is perpendicular to the plane defined by the satellite position and velocity vectors, and the radial direction is perpendicular to the along track and cross-track ones. The three components form a right-handed orthogonal system.

After applying corrections, the satellite position and clock is referred to the 'ionospheric free' phase center of the antenna which is compatible with the broadcast orbit reference.

The orbit and clock corrections do not include local effects like Ocean Loading, Solid Earth Tides or tropospheric delays. However, accurate single frequency applications can be correct for global ionospheric effects using so-call VTEC messages for global ionospheric state parameters.

While we have a plain ASCII standard for saving broadcast ephemeris in RINEX Navigation files, we don't have an equivalent standard for corrections to broadcast ephemeris. Hence BNC saves Broadcast Correction files following its own format definition. The filename convention for Broadcast Correction files follows the convention for RINEX Version 2 files except for the last character of the filename suffix which is set to 'C'.

BNC's Broadcast Correction files contain blocks of records in plain ASCII format. Each block covers information about one specific topic and starts with an 'Epoch Record'.

The 'Epoch Record' of a Broadcast Corrections block

The leading 'Epoch Record' of each block in a Broadcast Corrections file contains 11 parameters. Example:

> ORBIT 2015 06 17 11 43 35.0 2 53 CLK93

Their meaning is as follows:

1. Special character '>' is the first character in each 'Epoch Record' (as we have it in RINEX Version 3)
2. SSR message or topic descriptor, valid descriptors are:
   ORBIT, CLOCK, CODE_BIAS, PHASE_BIAS, or VTEC
3. Year, GPS time
4. Month, GPS time
5. Day, GPS time
6. Hour, GPS time
7. Minute, GPS time
8. Second, GPS time
9. SSR message update interval indicator
• 0 = 1 sec
• 1 = 2 sec
• 2 = 5 sec
• 3 = 10 sec
• 4 = 15 sec
• 5 = 30 sec
• 6 = 60 sec
• 7 = 120 sec
• 8 = 240 sec
• 9 = 300 sec
• 10 = 600 sec
• 11 = 900 sec
• 12 = 1800 sec
• 13 = 3600 sec
• 14 = 7200 sec
• 15 = 10800 sec
10. Number of following records in this block
11. Mountpoint, source/stream indicator

Example for block 'ORBIT' carrying orbit corrections

> ORBIT 2015 06 17 11 43 35.0 2 53 CLK93
G01   9     0.5134     0.3692     0.6784        0.0000    -0.0000    -0.0000
G02  25    57.6817   139.0492   -91.3456        0.5436    -0.6931     1.0173
G03  79   -32.1768   191.8368  -121.6540        0.2695     0.2296     0.4879
...
G32  82     1.8174     1.1704     0.2200       -0.0002    -0.0000    -0.0001
R01  59     0.7819    -0.6968     0.7388       -0.0001     0.0004     0.0004
R02  59     0.5816    -0.5800    -0.2004        0.0001    -0.0006     0.0001
R03  59     0.4635    -0.9104    -0.3832        0.0001     0.0001     0.0005
...
R24  59     0.5935     2.0732    -0.6884       -0.0000     0.0004     0.0003

Records in this block provide the following satellite specific information:

• GNSS Indicator and Satellite Vehicle Pseudo Random Number
• IOD referring to Broadcast Ephemeris set
• Radial Component of Orbit Correction to Broadcast Ephemeris [m]
• Along-track Component of Orbit Correction to Broadcast Ephemeris [m]
• Cross-track Component of Orbit Correction to Broadcast Ephemeris [m]
• Velocity of Radial Component of Orbit Correction to Broadcast Ephemeris [m/s]
• Velocity of Along-track Component of Orbit Correction to Broadcast Ephemeris [m/s]
• Velocity of Cross-track Component of Orbit Correction to Broadcast Ephemeris [m/s]

Example for block 'CLOCK' carrying clock corrections

> CLOCK 2015 06 17 11 43 35.0 2 53 CLK93
G01   9     0.5412     0.0000     0.0000
G02  25    11.1811     0.0000     0.0000
G03  79    45.0228     0.0000     0.0000
...
G32  82    -1.5324     0.0000     0.0000
R01  59     4.2194     0.0000     0.0000
R02  59     2.0535     0.0000     0.0000
R03  59     1.8130     0.0000     0.0000
...
R24  59     2.7409     0.0000     0.0000

Records in this block provide the following satellite specific information:

• GNSS Indicator and Satellite Vehicle Pseudo Random Number
• IOD referring to Broadcast Ephemeris set
• C0 polynomial coefficient for Clock Correction to Broadcast Ephemeris [m]
• C1 polynomial coefficient for Clock Correction to Broadcast Ephemeris [m/s]
• C2 polynomial coefficient for Clock Correction to Broadcast Ephemeris [m/s**2]

Example for block 'CODE_BIAS' carrying code biases

> CODE_BIAS 2015 06 17 11 43 35.0 2 53 CLK93
G01    5   1C    -3.3100   1W    -3.7500   2W    -6.1900   2X    -5.7800   5I    -5.4200
G02    5   1C     3.6000   1W     3.9300   2W     6.4800   2X     0.0000   5I     0.0000
G03    5   1C    -2.1600   1W    -2.6500   2W    -4.3600   2X    -4.4800   5I    -5.3400
...
G32    5   1C    -1.5800   1W    -1.1000   2W    -1.8200   2X     0.0000   5I     0.0000
R01    4   1C    -2.4900   1P    -2.4900   2C    -3.1500   2P    -4.1200
R02    4   1C     0.3900   1P     0.2100   2C     0.4000   2P     0.3400
R03    4   1C     2.4800   1P     2.2800   2C     3.7800   2P     3.7700
...
R24    4   1C     2.7000   1P     2.7800   2C     3.9800   2P     4.6000

Records in this block provide the following satellite specific information:

• GNSS Indicator and Satellite Vehicle Pseudo Random Number
• Number of Code Biases, succeeded by code specific information:
• Indicator to specify the signal and tracking mode
• Code Bias [m]
• Indicator to specify the signal and tracking mode
• Code Bias [m]
• etc.

Example for block 'PHASE_BIAS' carrying phase biases

> PHASE_BIAS 2015 06 17 11 43 35.0 2 31 CLK93
 0   1
G01 245.39062500   0.00000000    3   1C     3.9518   1   2   6   2W     6.3177   1   2   6   5I     6.8059   1   2   6
G02 250.31250000   0.00000000    3   1C    -4.0900   1   2   5   2W    -6.7044   1   2   5   5I     0.0000   1   2   5
G03 281.95312500   0.00000000    3   1C     2.9327   1   2   4   2W     4.6382   1   2   4   5I     5.4120   1   2   4
...
G32 290.39062500   0.00000000    3   1C     1.2520   1   2   5   2W     2.0554   1   2   5   5I     0.0000   1   2   5

The second record in this block provides the following consistency information:

• Dispersive bias consistency indicatory
  0 − phase biases valid for non-dispersive signal only
  1 − phase biases maintain consistency between non-dispersive and all original dispersive phase signals
• MW consistency indicator
  0 − code and phase biases are independently derived
  1 − consistency between code and phase biases is maintained for the MW combinations

• GNSS Indicator and Satellite Vehicle Pseudo Random Number
• Yaw angle [°], restricted to [0°... 360°]
• Yaw rate [°/s]
• Number of phase biases in this record, succeeded by phase specific information:
• Signal and tracking mode indicator
• Phase bias [m]
• Signal integer indicator
• Signal wide-lane integer indicator
• Signal discontinuity counter

Example for block 'VTEC' carrying ionospheric corrections

> VTEC 2015 06 17 11 43 35.0 6 1 CLK93
 1  6  6   450000.0
   17.6800     0.0000     0.0000     0.0000     0.0000     0.0000     0.0000
    4.5200     8.8700     0.0000     0.0000     0.0000     0.0000     0.0000
   -4.6850    -0.3050     1.1700     0.0000     0.0000     0.0000     0.0000
   -2.2250    -1.3900    -1.0250    -0.1300     0.0000     0.0000     0.0000
    0.8750    -0.3800     0.2700    -0.1300     0.0400     0.0000     0.0000
    1.2150     0.9050    -1.0100     0.3700    -0.1450    -0.2450     0.0000
   -0.8200     0.4850     0.2300    -0.1750     0.3400    -0.0900    -0.0400
    0.0000     0.0000     0.0000     0.0000     0.0000     0.0000     0.0000
    0.0000    -0.0700     0.0000     0.0000     0.0000     0.0000     0.0000
    0.0000     0.5800    -1.4150     0.0000     0.0000     0.0000     0.0000
    0.0000    -0.6200    -0.1500     0.2600     0.0000     0.0000     0.0000
    0.0000     0.0700    -0.0900    -0.0550     0.1700     0.0000     0.0000
    0.0000     0.5000     0.3050    -0.5700    -0.5250    -0.2750     0.0000
    0.0000     0.0850    -0.4700     0.0600     0.0700     0.1600     0.0400

The second record in this block provides four parameters:

• Layer number
• Maximum degree of spherical harmonics
• Maximum order of spherical harmonics
• Height of ionospheric layer [m]

• Spherical harmonic coefficients C and S, sorted by degree and order (0 to maximum)

Specify a directory for saving Broadcast Corrections in files. If the specified directory does not exist, BNC will not create Broadcast Correction files. Default value for Broadcast Corrections 'Directory' is an empty option field, meaning that no Broadcast Correction files will be created.

Select the length of the Broadcast Correction files. The default value is 1 day.

BNC can output epoch by epoch synchronized Broadcast Corrections in ASCII format on your local host (IP 127.0.0.1) through an IP 'Port'. Specify an IP port number to activate this function. The default is an empty option field, meaning that no Broadcast Correction output via IP port is generated.

The output format is similar to the format used for saving Broadcast Corrections in a file.

The following is an example output for the stream from mountpoint CLK93:

> ORBIT 2015 06 19 16 41 00.0 2 53 CLK93
G01  85     0.5891    -0.5124    -0.0216       -0.0001    -0.0002     0.0000
G02  25  -150.1820    11.4676    84.5216        0.4130    -0.6932     1.0159
G03  79    15.1999   141.9932  -156.4244        0.6782    -0.8607    -0.8211
...
G32  39     1.8454     0.4888    -0.3876       -0.0001    -0.0001     0.0001
R01  79    -0.0506     1.9024    -0.0120        0.0004     0.0002    -0.0000
R02  79     0.1623     0.9012     0.3984        0.0001     0.0001     0.0002
R03  79     0.3247    -2.6704    -0.0240        0.0005    -0.0002     0.0002
...
R24  79     0.7046    -0.5088    -0.0160       -0.0000     0.0000    -0.0002
> CLOCK 2015 06 19 16 41 00.0 2 53 CLK93
G01  85  -116.9441     0.0000     0.0000
G02  25  -110.4472     0.0000     0.0000
G03  79   -96.8299     0.0000     0.0000
...
G32  39  -119.2757     0.0000     0.0000
R01  79     1.5703     0.0000     0.0000
R02  79    -1.4181     0.0000     0.0000
R03  79     0.2072     0.0000     0.0000
...
R24  79     1.1292     0.0000     0.0000
> CODE_BIAS 2015 06 19 16 41 00.0 0 56 CLK93
E11    3   1B     1.3800   5Q     2.4800   7Q     2.5000
E12    3   1B     0.3900   5Q     0.6900   7Q     0.5300
E19    3   1B    -1.7800   5Q    -3.1900   7Q    -3.0700
G01    5   1C    -3.3100   1W    -3.7500   2W    -6.1900   2X    -5.7800   5I    -5.4200
G02    5   1C     3.6000   1W     3.9300   2W     6.4800   2X     0.0000   5I     0.0000
G03    5   1C    -2.1600   1W    -2.6500   2W    -4.3600   2X    -4.4800   5I    -5.3400
...
G32    5   1C    -1.5800   1W    -1.1000   2W    -1.8200   2X     0.0000   5I     0.0000
R01    4   1C    -2.4900   1P    -2.4900   2C    -3.1500   2P    -4.1200
R02    4   1C     0.3900   1P     0.2100   2C     0.4000   2P     0.3400
R03    4   1C     2.4800   1P     2.2800   2C     3.7800   2P     3.7700
...
R24    4   1C     2.7000   1P     2.7800   2C     3.9800   2P     4.6000
> PHASE_BIAS 2015 06 19 16 41 00.0 2 31 CLK93
 0   1
G01 309.37500000   0.00000000    3   1C     3.9922   1   2   6   2W     6.3568   1   2   6   5I     6.8726   1   2   6
G02 263.67187500   0.00000000    3   1C    -4.0317   1   2   7   2W    -6.6295   1   2   7   5I     0.0000   1   2   7
G03 267.89062500   0.00000000    3   1C     3.1267   1   2   4   2W     4.9126   1   2   4   5I     5.6478   1   2   4
...
G32 255.93750000   0.00000000    3   1C     1.3194   1   2   5   2W     2.1448   1   2   5   5I     0.0000   1   2   5
> VTEC 2015 06 19 16 41 00.0 6 1 CLK93
 1  6  6   450000.0
   16.7450     0.0000     0.0000     0.0000     0.0000     0.0000     0.0000 
    4.9300     8.1600     0.0000     0.0000     0.0000     0.0000     0.0000 
   -4.4900     0.2550     1.0950     0.0000     0.0000     0.0000     0.0000 
   -2.2450    -1.9500    -0.7950    -0.4700     0.0000     0.0000     0.0000 
    1.0250    -0.9000    -0.0900     0.1050     0.1450     0.0000     0.0000 
    1.5500     0.9750    -0.8150     0.3600     0.0350    -0.0900     0.0000 
   -0.4050     0.8300     0.0800    -0.0650     0.2200     0.0150    -0.1600 
    0.0000     0.0000     0.0000     0.0000     0.0000     0.0000     0.0000 
    0.0000    -0.1250     0.0000     0.0000     0.0000     0.0000     0.0000 
    0.0000     1.0050    -0.7750     0.0000     0.0000     0.0000     0.0000 
    0.0000    -0.2300     0.7150     0.7550     0.0000     0.0000     0.0000 
    0.0000    -0.4100    -0.1250     0.2400     0.2700     0.0000     0.0000 
    0.0000     0.0850    -0.3400    -0.0500    -0.2200    -0.0750     0.0000 
    0.0000     0.2000    -0.2850    -0.0150    -0.0250     0.0900     0.0650 

The source code for BNC comes with an example Perl script 'test_tcpip_client.pl' that allows you to read BNC's Broadcast Corrections from the IP port.

Figure 17: BNC configuration example for pulling, saving and output of Broadcast Corrections.

BNC can generate synchronized or unsynchronized observations epoch by epoch from all stations and satellites to feed a real-time GNSS network engine. Observations can be streamed out through an IP port and/or saved in a local file. The output is always in plain ASCII format and sorted per incoming stream.

Any epoch in the output begins with a line containing the GPS week number and the seconds within the GPS week. Following lines begin with the mountpoint string of the stream which provides the observations followed by a satellite ID. Observation types are specified by the three character observation code defined in RINEX Version 3. In case of phase observations a Slip Count is added which is put to "-1" if it is not set. The end of an epoch in indicated by an empty line.

Note on 'Slip Count':
It is the current understanding of BNC's authors that different Slip Counts could be referred to different phase measurements (i.e. L1C and L1P). The 'loss-of-lock' flags in RINEX are an example for making such kind of information available per phase measurement. However, it looks like we do have only one Slip Count in RTCM Version 3 for all phase measurements. As it could be that a receiver generates different Slip Counts for different phase measurements, we output one Slip Count per phase measurement to a listening real-time GNSS network engine.

The following is an example for file and IP port output which presents observations from GPS, GLONASS, Galileo, BDS (BeiDou), QZSS, and SBAS satellites as collected through streams WTZR0, CUT07, and COCO0:

> 1850 120556.0000000
WTZR0 G01  C1C   25394034.112 L1C  133446552.870 127 S1C   43.000 C2W   25394040.832 L2W  103984354.397 127 S2W   34.750
WTZR0 G12  C1C   21452585.278 L1C  112734165.968 127 S1C   50.500 C2W   21452584.578 L2W   87844835.675 127 S2W   46.250
WTZR0 G13  C1C   24061255.720 L1C  126442693.941 127 S1C   45.750 C2W   24061259.860 L2W   98526745.844 127 S2W   35.500
...
WTZR0 G28  C1C   25200320.952 L1C  132428507.619 127 S1C   43.500 C2W   25200323.952 L2W  103191035.510 127 S2W   35.000
WTZR0 R01  C1C   21380903.420 L1C  114293200.377 127 S1C   48.750 C2P   21380907.340 L2P   88894741.570 127 S2P   41.500
WTZR0 R02  C1C   22644814.432 L1C  120837082.440 127 S1C   46.500 C2P   22644817.592 L2P   93984421.793 127 S2P   42.500
WTZR0 R08  C1C   23068202.108 L1C  123529160.309 127 S1C   46.500 C2P   23068204.988 L2P   96078225.806 127 S2P   41.750
...
WTZR0 R21  C1C   23024132.668 L1C  123206823.917 127 S1C   47.250 C2P   23024137.748 L2P   95827547.481 127 S2P   42.000
CUT07 G02  C1C   23272399.734 L1C  122297070.388 597 D1C        -87.977 S1C   42.312 C2W   23272400.234 L2W   95297219.119 597 S2W   26.688
CUT07 G03  C1C   24110497.680 L1C  126701879.242 659 D1C      -3056.984 S1C   37.875 C2W   24110505.621 L2W   98728694.271 659 S2W   21.688 C2X   24110505.926 L2X   98728386.267 659 S2X   40.312 C5X   24110510.094 L5X   94614774.123 659 S5X   45.312
CUT07 G05  C1C   24944957.625 L1C  131087212.915 520 D1C       3895.703 S1C   37.625 C2W   24944962.168 L2W  102145324.192 520 S2W   20.875 C2X   24944962.004 L2X  102145177.172 520 S2X   36.125
...
CUT07 G30  C1C   20928146.555 L1C  109978415.517 606 D1C       2025.395 S1C   54.000 C2W   20928151.566 L2W   85697602.266 606 S2W   43.188 C2X   20928151.930 L2X   85697012.264 606 S2X   49.875 C5X   20928155.511 L5X   82126237.098 606 S5X   55.812
CUT07 R04  C1C   22160327.953 L1C  118666825.671 652 D1C      -2522.773 S1C   46.375 C1P   22160327.797 L1P  118667617.662 652 S1P   45.188 C2C   22160332.254 L2C   92297583.036 652 S2C   43.625 C2P   22160332.567 L2P   92297422.037 652 S2P   42.312
CUT07 R05  C1C   19447023.836 L1C  103954847.683 632 D1C        379.031 S1C   48.500 C1P   19447023.914 L1P  103954847.676 632 S1P   47.000 C2C   19447027.547 L2C   80853787.461 632 S2C   50.500 C2P   19447028.449 L2P   80853787.472 632 S2P   49.875
CUT07 R06  C1C   21207223.649 L1C  113165770.921 587 D1C       3560.348 S1C   50.875 C1P   21207223.375 L1P  113166378.915 587 S1P   49.125 C2C   21207227.008 L2C   88017617.177 587 S2C   46.000 C2P   21207228.262 L2P   88017377.180 587 S2P   45.500
...
CUT07 R16  C1C   19585043.860 L1C  104620582.766 598 D1C       2187.578 S1C   53.312 C1P   19585044.758 L1P  104620582.776 598 S1P   51.375 C2C   19585048.981 L2C   81371454.856 598 S2C   49.375 C2P   19585049.879 L2P   81371454.858 598 S2P   48.812
CUT07 E20  C1X   27365616.429 L1X  143807095.898 527 D1X       2876.149 S1X   35.000
CUT07 S27  C1C   39931452.594 L1C  209841056.112 679 D1C        406.422 S1C   39.000 C5I   39931443.285 L5I  156699444.322 679 S5I   42.375
CUT07 S28  C1C   37844752.406 L1C  198874711.984 683 D1C        407.059 S1C   46.625 C5I   37844741.785 L5I  148510882.534 704 S5I   45.000
CUT07 S29  C1C   37651158.016 L1C  197858052.600 683 D1C        403.512 S1C   43.000
CUT07 S37  C1C   37651147.828 L1C  197858448.618 683 D1C        403.531 S1C   41.625
CUT07 J01  C1C   40048292.047 L1C  210455903.893 704 D1C      -1583.379 S1C   41.812 C1Z   40048289.996 L1Z  210455441.428 704 S1Z   40.875 C6L   40048292.316 L6L  170824217.096 704 S6L   37.000 C2X   40048298.183 L2X  163991247.082 704 S2X   40.688 C5X   40048303.817 L5X  157158277.377 704 S5X   46.375 C1X   40048292.351 L1X  210455442.883 704 S1X   44.000
CUT07 C01  C2I   37324042.141 L2I  194356552.952 704 D2I        440.996 S2I   42.688 C6I   37324028.519 L6I  157929660.388 704 S6I   45.875 C7I   37324033.363 L7I  150287901.788 704 S7I   46.312
CUT07 C02  C2I   38275575.024 L2I  199310999.358 704 D2I        404.117 S2I   37.875 C6I   38275566.211 L6I  161956457.229 704 S6I   43.000 C7I   38275569.942 L7I  154119870.634 704 S7I   42.312
CUT07 C03  C2I   37135200.797 L2I  193371988.170 692 D2I        431.973 S2I   43.312 C6I   37135190.051 L6I  157131416.391 692 S6I   48.000 C7I   37135194.422 L7I  149528282.423 692 S7I   46.812
...
CUT07 C10  C2I   36760375.289 L2I  191420952.281 640 D2I       1025.387 S2I   45.688 C6I   36760364.426 L6I  155545258.984 640 S6I   46.688 C7I   36760373.723 L7I  148018880.533 640 S7I   46.312
COCO0 G02  C1C   22476261.427 L1C  118113589.570 586 D1C       1412.187 S1C   44.938 C2W   22476260.826 L2W   92036575.260 586 D2W       1100.406 S2W   35.312
COCO0 G03  C1C   24341919.159 L1C  127917554.810 663 D1C      -2074.090 S1C   38.688 C2W   24341930.673 L2W   99676015.236 663 D2W      -1616.167 S2W   24.438 C2L   24341930.723 L2L   99676013.201 662 D2L      -1616.219 S2L   38.750 C5Q   24341933.159 L5Q   95522839.465 662 D5Q      -1548.741 S5Q   42.875
COCO0 G05  C1C   25474658.679 L1C  133870244.277 493 D1C       3159.081 S1C   39.438 C2W   25474663.398 L2W  104314491.669 491 D2W       2461.609 S2W   24.562
...
COCO0 G30  C1C   20331006.470 L1C  106840352.867 617 D1C       -212.495 S1C   52.188 C2W   20331010.207 L2W   83252324.005 617 D2W       -165.585 S2W   49.500 C2L   20331010.394 L2L   83252323.011 613 D2L       -165.567 S2L   50.250
COCO0 R04  C1C   23325683.508 L1C  124907994.343 660 D1C       -873.812 S1C   41.125 C2C   23325691.864 L2C   97150681.177 660 D2C       -679.608 S2C   42.312 C2P   23325691.726 L2P   97150688.171 660 D2P       -679.605 S2P   43.188
COCO0 R05  C1C   21328759.151 L1C  114014512.115 644 D1C       1069.493 S1C   42.812 C2C   21328765.687 L2C   88678051.219 647 D2C        831.814 S2C   47.812 C2P   21328765.883 L2P   88678030.225 645 D2P        831.850 S2P   47.438
COCO0 R09  C1C   21027128.207 L1C  112283840.462 555 D1C       3490.368 S1C   45.188
...
COCO0 R21  C1C   23445025.787 L1C  125459055.095 555 D1C       -765.275 S1C   42.688 C2C   23445033.733 L2C   97579294.654 555 D2C       -595.265 S2C   40.188 C2P   23445033.487 L2P   97579294.651 537 D2P       -595.197 S2P   40.875
COCO0 J01  C1C   39927130.880 L1C  209818564.350 704 D1C      -1175.392 S1C   41.562 C2L   39927135.634 L2L  163495064.612 704 D2L       -915.829 S2L   40.562 C5Q   39927138.784 L5Q  156682808.818 704 D5Q       -877.788 S5Q   44.375
COCO0 C01  C2I   37949052.545 L2I  197610628.940 704 D2I        179.818 S2I   44.500 C7I   37949047.569 L7I  152805027.848 704 D7I        139.094 S7I   46.812
COCO0 C02  C2I   36636436.522 L2I  190775621.693 704 D2I        166.143 S2I   48.188 C7I   36636433.422 L7I  147519844.394 704 D7I        128.449 S7I   50.625
COCO0 C03  C2I   36481125.870 L2I  189966778.019 666 D2I        178.936 S2I   48.688 C7I   36481123.342 L7I  146894352.298 653 D7I        138.364 S7I   50.312
...
COCO0 C10  C2I   35632229.616 L2I  185546695.648 704 D2I        327.212 S2I   49.625 C7I   35632229.807 L7I  143476633.351 704 D7I        252.998 S7I   50.812

> 1850 120557.0000000
...

The source code for BNC comes with a Perl script named 'test_tcpip_client.pl' that allows you to read BNC's (synchronized or unsynchronized) ASCII observation output from the IP port and print it on standard output.

Note that any socket connection of an application to BNC's synchronized or unsynchronized observations ports is recorded in the 'Log' tab on the bottom of the main window together with a connection counter, resulting in log records like 'New client connection on sync/usync port: # 1'.

The following figure shows the screenshot of a BNC configuration where a number of streams is pulled from different Ntrip Broadcasters to feed a GNSS engine via IP port output.

Figure 18: Synchronized BNC output via IP port to feed a GNSS real-time engine.

BNC can produce synchronized observations in ASCII format on your local host (IP 127.0.0.1) through an IP 'Port'. Synchronized means that BNC collects all observation data for any specific epoch which become available within a certain number of latency seconds (see 'Wait for Full Obs Epoch' option). It then - epoch by epoch - outputs whatever has been received. The output comes block wise per stream. Specify an IP port number here to activate this function. The default is an empty option field, meaning that no binary synchronized output is generated.

When feeding a real-time GNSS network engine waiting for synchronized observations epoch by epoch, BNC drops whatever is received later than 'Wait for full obs epoch' seconds. A value of 3 to 5 seconds could be an appropriate choice for that, depending on the latency of the incoming streams and the delay acceptable for your real-time GNSS product. Default value for 'Wait for full obs epoch' is 5 seconds.

Note that 'Wait for full obs epoch' does not affect the RINEX Observation file content. Observations received later than 'Wait for full obs epoch' seconds will still be included in the RINEX Observation files.

Select the synchronized observation output sampling interval in seconds. A value of zero '0' tells BNC to send/store all received epochs. This is the default value.

Specify the full path to a 'File' where synchronized observations are saved in plain ASCII format. The default value is an empty option field, meaning that no ASCII output file is created.

Beware that the size of this file can rapidly increase depending on the number of incoming streams. The name of the file can be changed on-the-fly, to prevent it from becoming too large. This option is primarily meant for testing and evaluation.

BNC can produce unsynchronized observations from all configured streams in ASCII format on your local host (IP 127.0.0.1) through an IP 'Port'. Unsynchronized means that BNC immediately forwards any received observation to the port. Nevertheless, the output comes block wise per stream. Specify an IP port number here to activate this function. The default is an empty option field, meaning that no unsynchronized output is generated.

You may use BNC to feed a serial connected device like a GNSS receiver. For that an incoming stream can be forwarded to a serial port. Depending on the stream contents the receiver may use it for Differential GNSS, Precise Point Positioning or any other purpose supported by its firmware.

Note that receiving a VRS stream requires the receiver sending NMEA sentences (mode 'Manual' or 'Auto') to the Ntrip Broadcaster. The following figure shows the data flow when pulling a VRS stream or a physical (none-VRS) stream.

Figure 19: Flowcharts, BNC forwarding a stream to a serial connected receiver; sending NMEA sentences is mandatory for VRS streams.

The following figure shows the screenshot of an example situation where BNC pulls a VRS stream from an Ntrip Broadcaster to feed a serial connected RTK rover.

Figure 20: BNC pulling a VRS stream to feed a serial connected RTK rover.

Enter a 'Mountpoint' to forward its corresponding stream to a serial connected GNSS receiver.

When selecting one of the serial communication options listed below, make sure that you pick those configured to the serial connected receiver.

Enter the serial 'Port name' selected on your host for communication with the serial connected receiver. Valid port names are

   Windows:       COM1, COM2
   Linux:         /dev/ttyS0, /dev/ttyS1
   FreeBSD:       /dev/ttyd0, /dev/ttyd1
   Digital Unix:  /dev/tty01, /dev/tty02
   HP-UX:         /dev/tty1p0, /dev/tty2p0
   SGI/IRIX:      /dev/ttyf1, /dev/ttyf2
   SunOS/Solaris: /dev/ttya, /dev/ttyb

Note that you must plug a serial cable in the port defined here before you start BNC.

Select a 'Baud rate' for the serial output link. Note that using a high baud rate is recommended.

Select a 'Flow control' for the serial output link. Note that your selection must equal the flow control configured to the serial connected device. Select 'OFF' if you don't know better.

Select the 'Parity' for the serial output link. Note that parity is often set to 'NONE'.

Select the number of 'Data bits' for the serial output link. Note that often '8' data bits are used.

Select the number of 'Stop bits' for the serial output link. Note that often '1' stop bit is used.

The 'NMEA' option supports the so-called 'Virtual Reference Station' (VRS) concept which requires the receiver to send approximate position information to the Ntrip Broadcaster. Select 'no' if you don't want BNC to forward or upload any NMEA message to the Ntrip broadcaster in support of VRS.

Select 'Auto' to automatically forward NMEA messages of type GGA from your serial connected receiver to the Ntrip broadcaster and/or save them in a file.

Select 'Manual GPGGA' or 'Manual GNGGA' if you want BNC to produce and upload GPGGA or GNGGA NMEA messages to the Ntrip broadcaster because your serial connected receiver doesn't generate these messages. A Talker ID 'GP' preceding the GGA string stands for GPS solutions while a Talker ID 'GN' stands for multi constellation solutions.

Note that selecting 'Auto' or 'Manual' works only for VRS streams which show up under the 'Streams' canvas on BNC's main window with 'nmea' stream attribute set to 'yes'. This attribute is either extracted from the Ntrip broadcaster's source-table or introduced by the user through editing the BNC configuration file.

Specify the full path to a file where NMEA messages coming from your serial connected receiver are saved. Default is an empty option field, meaning that no NMEA messages will be saved on disk.

Specify an approximate 'Height' above mean sea level in meters for the reference station introduced through 'Mountpoint'. Together with the latitude and longitude from the Ntrip broadcaster source-table the height information is used to build GGA messages to be sent to the Ntrip broadcaster.

For adjusting latitude and longitude values of a VRS stream given in the 'Streams' canvas you can double click the latitude/longitude data fields, specify appropriate values and then hit Enter.

This option is only relevant when option 'NMEA' is set to 'Manual GPGGA' or 'Manual GNGGA' respectively.

Select a sampling interval in seconds for manual generation and upload of NMEA GGA sentences.

A sampling rate of '0' means, that a GGA sentence will be send only once to initialize the requested VRS stream. Note that some VRS systems need GGA sentences at regular intervals.

At any time an incoming stream might become unavailable or corrupted. In such cases, it is important that the BNC operator and/or the stream providers become aware of the situation so that necessary measures can be taken to restore the stream. Furthermore, continuous attempts to decode a corrupted stream can generate unnecessary workload for BNC. Outages and corruptions are handled by BNC as follows:

Stream outages: BNC considers a connection to be broken when there are no incoming data detected for more than 20 seconds. When this occurs, BNC will attempt to reconnect at a decreasing rate. It will first try to reconnect with 1 second delay and again in 2 seconds if the previous attempt failed. If the attempt is still unsuccessful, it will try to reconnect within 4 seconds after the previous attempt and so on. The wait time doubles each time with a maximum wait time of 256 seconds.

Stream corruption: Not all bits chunk transfers to BNC's internal decoders return valid observations. Sometimes several chunks might be needed before the next observation can be properly decoded. BNC buffers all the outputs (both valid and invalid) from the decoder for a short time span (size derived from the expected 'Observation rate') and then determines whether a stream is valid or corrupted.

Outage and corruption events are reported in the 'Log' tab. They can also be passed on as parameters to a shell script or batch file to generate an advisory note to BNC operator or affected stream providers. This functionality lets users utilize BNC as a real-time performance monitor and alarm system for a network of GNSS reference stations.

BNC can collect all returns (success or failure) coming from a decoder within a certain short time span to then decide whether a stream has an outage or its content is corrupted. This procedure needs a rough a priori estimate of the expected observation rate of the incoming streams.

An empty option field (default) means that you don't want explicit information from BNC about stream outages and incoming streams that cannot be decoded.

Event 'Begin_Failure' will be reported if no data is received continuously for longer than the 'Failure threshold' time. Similarly, event 'Begin_Corrupted' will be reported when corrupted data is detected by the decoder continuously for longer than this 'Failure threshold' time. The default value is set to 15 minutes and is recommended so not to inundate user with too many event reports.

Note that specifying a value of zero '0' for the 'Failure threshold' will force BNC to report any stream failure immediately. Note also that for using this function you need to specify the 'Observation rate'.

Once a 'Begin_Failure' or 'Begin_Corrupted' event has been reported, BNC will check for when the stream again becomes available or uncorrupted. Event 'End_Failure' or 'End_Corrupted' will be reported as soon as valid observations are again detected continuously throughout the 'Recovery threshold' time span. The default value is set to 5 minutes and is recommended so not to inundate users with too many event reports.

Note that specifying a value of zero '0' for the 'Recovery threshold' will force BNC to report any stream recovery immediately. Note also that for using this function you need to specify the 'Observation rate'.

As mentioned previously, BNC can trigger a shell script or a batch file to be executed when one of the events described are reported. This script can be used to email an advisory note to network operator or stream providers. To enable this feature, specify the full path to the script or batch file in the 'Script' field. The affected stream's mountpoint and type of event reported ('Begin_Outage', 'End_Outage', 'Begin_Corrupted' or 'End_Corrupted') will then be passed on to the script as command line parameters (%1 and %2 on Windows systems or $1 and $2 on Unix/Linux/Mac OS X systems) together with date and time information.

Leave the 'Script' field empty if you do not wish to use this option. An invalid path will also disable this option.

Examples for command line parameter strings passed on to the advisory 'Script' are:

   FFMJ0 Begin_Outage 08-02-21 09:25:59
   FFMJ0 End_Outage 08-02-21 11:36:02 Begin was 08-02-21 09:25:59

Sample script for Unix/Linux/Mac OS X systems:

   #!/bin/bash
   sleep $((60*RANDOM/32767))
   cat > mail.txt <<EOF
   Advisory Note to BNC User,
   Please note the following advisory received from BNC.
   Stream: $*
   Regards, BNC
   EOF
   mail -s "NABU: $1" email@address < mail.txt

Note the sleep command in this script which causes the system to wait for a random period of up to 60 seconds before sending the email. This should avoid overloading your mail server in case of a simultaneous failure of many streams.

This section describes several miscellaneous options which can be applied to a single stream (mountpoint) or to all configured streams.

The following figure shows RTCM message numbers and observation types contained in stream 'CUT07' and the message latencies recorded every 2 seconds.

Figure 21: RTCM message numbers, latencies and observation types.

Specify a mountpoint to apply one or several of the 'Miscellaneous' options to the corresponding stream. Enter 'ALL' if you want to apply these options to all configured streams. An empty option field (default) means that you don't want BNC to apply any of these options.

BNC can average latencies per stream over a certain period of GPS time, the 'Log latency' interval. Mean latencies are calculated from the individual latencies of one (first incoming) observation or Broadcast Correction per second. The mean latencies are then saved in BNC's logfile. Note that computing correct latencies requires the clock of the host computer to be properly synchronized. Note further that visualized latencies from the 'Latency' tab on the bottom of the main window represent individual latencies and not the mean latencies for the logfile.

Latency: Latency is defined in BNC by the following equation:

    UTC time provided by BNC's host
  - GPS time of currently processed epoch
  + Leap seconds between UTC and GPS time
  --------------
  = Latency

Statistics: BNC counts the number of GPS seconds covered by at least one observation. It also estimates an observation rate (independent from the a priori specified 'Observation rate') from all observations received throughout the first full 'Log latency' interval. Based on this rate, BNC estimates the number of data gaps when appearing in subsequent intervals.

Latencies of observations or corrections to Broadcast Ephemeris and statistical information can be recorded in the 'Log' tab at the end of each 'Log latency' interval. A typical output from a 1 hour 'Log latency' interval would be:

08-03-17 15:59:47 BRUS0: Mean latency 1.47 sec, min 0.66, max 3.02, rms 0.35, 3585 epochs, 15 gaps

Select a 'Log latency' interval to activate this function or select the empty option field if you do not want BNC to log latencies and statistical information.

When configuring a GNSS receiver for RTCM stream generation, the firmware's setup interface may not provide details about RTCM message types and observation types. As reliable information concerning stream contents should be available i.e. for Ntrip Broadcaster operators to maintain the broadcaster's source-table, BNC allows to scan RTCM streams for incoming message types and printout some of the contained meta-data. Contained observation types are also printed because such information is required a priori for the conversion of RTCM Version 3 MSM streams to RINEX Version 3 files. The idea for this option arose from 'inspectRTCM', a comprehensive stream analyzing tool written by D. Stoecker.

Tick 'Scan RTCM' to scan RTCM Version 2 or 3 streams and log all contained

• Numbers of incoming message types
• Antenna Reference Point (ARP) coordinates
• Antenna Phase Center (APC) coordinates
• Antenna height above marker
• Antenna descriptor.

• RINEX Version 3 Observation Types

Note that in RTCM Version 2 the message types 18 and 19 carry only the observables of one frequency. Hence it needs two type 18 and 19 messages per epoch to transport the observations from dual frequency receivers.

Please note further that RTCM Version 3 message types 1084 for GLONASS don't contain GLONASS channel numbers. Observations from these messages can only be decoded when you include 1020 GLONASS ephemeris messages to your stream which contain the channels. You could also consider adding a second stream carrying 1087 GLONASS observation messages or 1020 GLONASS ephemeris messages as both contain the GLONASS channel numbers.

Logged time stamps refer to message reception time and allow understanding repetition rates. Enter 'ALL' if you want to log this information from all configured streams. Beware that the size of the logfile can rapidly increase depending on the number of incoming RTCM streams.

This option is primarily meant for testing and evaluation. Use it to figure out what exactly is produced by a specific GNSS receiver's configuration. An empty option field (default) means that you don't want BNC to print the message type numbers and antenna information carried in RTCM streams.

BNC can output streams related to the above specified 'Mountpoint' through a TCP/IP port of your local host. Enter a port number to activate this function. The stream contents remains untouched. BNC does not decode or reformat the data.

Be careful when keyword 'ALL' is specified as 'Mountpoint' for involving all incoming streams together because the affiliation of data to certain streams gets lost in the output.

An empty option field (default) means that you don't want BNC to apply the TCP/IP port output option.

BNC can derive coordinates for rover positions following the Precise Point Positioning (PPP) approach. It uses either code or code plus phase data from one or more GNSS systems in ionosphere-free linear combinations P3 or L3. Besides pulling streams of observations from dual frequency GNSS receiver, this also

• Requires pulling in addition a stream carrying satellite orbit and clock corrections to Broadcast Ephemeris in the form of RTCM Version 3 'State Space Representation' (SSR) messages. Note that for BNC these Broadcast Corrections need to be referred to the satellite's Antenna Phase Center (APC). Streams providing such messages are listed on http://igs.bkg.bund.de/ntrip/orbits. Stream 'CLK11' on Ntrip Broadcaster 'products.igs-ip.net:2101' is an example.
• May require pulling a stream carrying Broadcast Ephemeris available as RTCM Version 3 message types 1019, 1020, 1043, 1044, 1045, 1046 and 63 (tentative). This becomes a must only when the stream coming from the receiver does not contain Broadcast Ephemeris or provides them only at very low repetition rate. Streams providing such messages are listed on http://igs.bkg.bund.de/ntrip/ephemeris. Stream 'RTCM3EPH' on caster 'products.igs-ip.net:2101' is an example.

When using the PPP option, it is important to understand which effects are corrected by BNC.

• BNC does correct for Solid Earth Tides and Phase Windup.
• Satellite antenna phase center offsets are corrected.
• Satellite antenna phase center variations are neglected because this is a small effect usually less than 2 centimeters.
• Observations can be corrected for a Receiver Antenna Offset. Depending on whether or not this correction is applied, the estimated position is either that of the receiver's antenna phase center or that of the receiver's Antenna Reference Point.
• Receiver antenna phase center variations are not included in the model. The bias caused by this neglect depends on the receiver antenna type. For most antennas it is smaller than a few centimeters.
• Ocean and atmospheric loading is neglected. Atmospheric loading is pretty small. Ocean loading is usually also a small effect but may reach up to about 10 centimeters for coastal stations.
• Rotational deformation due to polar motion (Polar Tides) is not corrected because this is a small effect usually less than 2 centimeters.

The provider of an orbit/clock corrections stream may switch with his service at any time from a duty to a backup server installation. This shall be noted in the SSR stream through a change of the Issue Of Data (IOD SSR) parameter. The PPP option in BNC will immediately reset all ambiguities in such a situation.

PPP options are specified in BNC through the following four panels.

• PPP (1): Input and output, specifying real-time or post processing mode and associated data sources
• PPP (2): Processed stations, specifying sigmas and noise of a priori coordinates and NMEA stream output
• PPP (3): Processing options, specifying general PPP processing options
• PPP (4): Plots, specifying visualization through time series and track maps

This panel provides options for specifying the input and output streams and files required by BNC for real-time or post processing PPP.

Figure 22: Real-time Precise Point Positioning with BNC, PPP Panel 1.

Choose between input from 'Real-time Streams' or 'RINEX Files' for PPP with BNC in real-time or post processing mode.

Real-time Streams
When choosing 'Real-time Streams' BNC will do PPP solutions in real-time. This requires pulling GNSS observation streams, Broadcast Ephemeris messages and a stream containing corrections to Broadcast Ephemeris. Streams must come in RTCM Version 2 or RTCM Version 3 format.

If you don't pull Broadcast Corrections BNC will switch with its solution to 'Single Point Positioning' (SPP) mode.

RINEX Files
This input mode allows you to specify RINEX Observation, RINEX Navigation and Broadcast Correction files. BNC accepts RINEX Version 2 as well as RINEX Version 3 Observation or Navigation file formats. Files carrying Broadcast Corrections must have the format produced by BNC through the 'Broadcast Corrections' panel.

Specifying only a RINEX Observation and a RINEX Navigation file and no Broadcast Corrections file leads BNC to a 'Single Point Positioning' (SPP) solution.

Debugging
Note that for debugging purposes BNC's real-time PPP functionality can also be used offline. Apply the 'File Mode' 'Command Line' option for that to read a file containing synchronized observations, orbit and clock correctors, and Broadcast Ephemeris. Example:

   bnc.exe --conf c:\temp\PPP.bnc --file c:\temp\RAW

Specify a RINEX Observation file. The file format can be RINEX Version 2 or RINEX Version 3.

Specify a RINEX Navigation file. The file format can be RINEX Version 2 or RINEX Version 3.

Specify a Broadcast 'Correction files' as saved beforehand using BNC. The file contents is basically the ASCII representation of a RTCM Version 3 Broadcast Correction (SSR) stream.

If you don't specify a 'Correction file' BNC will fall back from a PPP solution to a Single Point Positioning (SPP) solution.

Specify a Broadcast 'Corrections stream' from the list of selected 'Streams' you are pulling if you want BNC to correct your satellite ephemeris accordingly. Note that the stream's orbit and clock corrections must refer to the satellite Antenna Phase Center (APC). Streams providing such corrections are made available e.g. through the International GNSS Service (IGS) and listed on http://igs.bkg.bund.de/ntrip/orbits. The stream format must be RTCM Version 3 containing so-called SSR messages. Streams 'IGS03' and 'CLK11' supporting GPS plus GLONASS are examples.

If you don't specify a 'Corrections stream' BNC will fall back from a PPP solution to a Single Point Positioning (SPP) solution.

Enter the full path to an ASCII file which specifies all streams or files from stationary or mobile receivers you potentially may want to process. Specifying a 'Coordinates' file is optional. If it exists, it should contain one record per stream or file with the following parameters separated by blank characters:

• Input data source, to be specified either through
  • the 'Mountpoint' of an RTCM stream (when in real-time PPP mode), or
  • the first four characters of the RINEX observations file (when in post processing PPP mode).
  Having this parameter first in each record is mandatory. BNC can carry out PPP solutions only for streams or files specified here.


• Only for static observations from a stationary receiver:
  Approximate a priori XYZ coordinate [m] of the station's marker; specify '0.0 0.0 0.0' if unknown or when observations come from a mobile receiver.


• Nort, East and Up component [m] of antenna eccentricity which is the difference between Antenna Reference Point (ARP) and a nearby marker position; when specifying the antenna eccentricity BNC will produce coordinates referring to the marker position and not referring to ARP; specify '0.0 0.0 0.0' if eccentricity is unknown or the ARP itself is understood as the marker.


• Receiver's antenna name as defined in your ANTEX file (see below); Observations will be corrected for the Antenna Phase Center (APC) offsets and variations which may result in a reduction of a few centimeters at max; the specified name must consist of 20 characters; add trailing blanks if the antenna name has less than 20 characters; examples:
  

     'JPSREGANT_SD_E      ' (no radome)
     'LEIAT504        NONE' (no radome)
     'LEIAR25.R3      LEIT' (radome)

  Leave antenna name blank if you don't want to correct observations for APC offsets and variations or if you don't know the antenna name.

Records in the 'Coordinates' file with exclamation mark '!' in the first column or blank records will be understood as comment lines and ignored.

The following is an example contents for a 'Coordinates' file. Here each record describes the mountpoint of a stream available from the global IGS real-time reference station network. A priori coordinates are followed by North/East/Up eccentricity components of the ARP followed by the antenna name and radome in use.

!
! Station    X[m]          Y[m]          Z[m] North[m]  EAST[m]  UP[m]  Antenna        Radom
! -------------------------------------------------------------------------------------------
ADIS0  4913652.6612  3945922.7678   995383.4359  0.0000  0.0000  0.0010 TRM29659.00     NONE
ALIC0 -4052052.5593  4212836.0078 -2545104.8289  0.0000  0.0000  0.0015 LEIAR25.R3      NONE
BELF0  3685257.8823  -382908.8992  5174311.1067  0.0000  0.0000  0.0000 LEIAT504GG      LEIS
BNDY0 -5125977.4106  2688801.2966 -2669890.4345  0.0000  0.0000  0.0000 ASH701945E_M    NONE
BRAZ0  4115014.0678 -4550641.6105 -1741443.8244  0.0000  0.0000  0.0080 LEIAR10         NONE
CAGZ0  4893379.8326   772650.6854  4004180.1625  0.0000  0.0000  0.0945 JPSREGANT_DD_E  NONE
CALG0 -1635378.1748 -3665371.5746  4941664.3370  0.0000  0.0000  0.0000 SOK702          NONE
CONZ0  1492004.6119 -4887911.2671 -3803640.2397  0.0000  0.0000  0.0574 LEIAR25.R3      LEIT
CTWN0  5023564.4285  1677795.7211 -3542025.8392  0.0000  0.0000  0.0000 ASH701941.B     NONE
CUT07 -2364337.4408  4870285.6055 -3360809.6280  0.0000  0.0000  0.0000 TRM59800.00     SCIS
DHLG3 -2319099.4261 -4799846.4583  3490090.4018  0.0000  0.0000  0.1224 ASH701945B_M    SCIS
FAA10 -5247393.4678 -3076866.6580 -1911521.1749  0.0000  0.0000  0.1262 LEIAR25.R4      NONE
GANP0  3929181.3480  1455236.9105  4793653.9880  0.0000  0.0000  0.3830 TRM55971.00     NONE
HLFX0  2018905.6037 -4069070.5095  4462415.4771  0.0000  0.0000  0.1000 TPSCR.G3        NONE
KIRU0  2251420.6255   862817.3340  5885476.8395  0.0000  0.0000  0.0620 ASH701945C_M    SNOW
LHAZ0  -106941.9272  5549269.8041  3139215.1564  0.0000  0.0000  0.1330 ASH701941.B     NONE
LMMF7  2993387.3587 -5399363.8649  1596748.0983  0.0000  0.0000  0.0000 TRM57971.00     NONE
MAO07 -5466067.0979 -2404333.0198  2242123.1929  0.0000  0.0000  0.0000 LEIAR25.R3      LEIT
NICO0  4359415.5252  2874117.1872  3650777.9614  0.0000  0.0000  0.0650 LEIAR25.R4      LEIT
NKLG7  6287385.7320  1071574.7606    39133.1088 -0.0015 -0.0025  3.0430 TRM59800.00     SCIS
NURK7  5516756.5103  3196624.9684  -215027.1315  0.0000  0.0000  0.1300 TPSCR3_GGD      NONE
OHIX7  1525809.2353 -2432478.7568 -5676166.2639  0.0000  0.0000  0.0660 LEIAR25.R4      LEIT
ONSA0  3370658.3928   711877.2903  5349787.0603  0.0000  0.0000  0.9950 AOAD/M_B        OSOD
PDEL0  4551595.9072 -2186892.9495  3883410.9685  0.0000  0.0000  0.0000 LEIAT504GG      NONE
RCMN0  5101056.6270  3829074.4206  -135016.1589  0.0000  0.0000  0.0000 LEIAT504GG      LEIS
REUN0  3364098.9668  4907944.6121 -2293466.7379  0.0000  0.0000  0.0610 TRM55971.00     NONE
REYK7  2587384.0890 -1043033.5433  5716564.1301  0.0000  0.0000  0.0570 LEIAR25.R4      LEIT
RIO27  1429907.8578 -3495354.8953 -5122698.5595  0.0000  0.0000  0.0350 ASH700936C_M    SNOW
SMR50   927077.1096 -2195043.5597 -5896521.1344  0.0000  0.0000  0.0000 TRM41249.00     TZGD
SUWN0 -3062023.1604  4055447.8946  3841818.1684  0.0000  0.0000  1.5700 TRM29659.00     DOME
TASH7  1695944.9208  4487138.6220  4190140.7391  0.0000  0.0000  0.1206 JAV_RINGANT_G3T NONE
UFPR0  3763751.6731 -4365113.9039 -2724404.5331  0.0000  0.0000  0.1000 TRM55971.00     NONE
UNB30  1761287.9724 -4078238.5659  4561417.8448  0.0000  0.0000  0.3145 TRM57971.00     NONE
VILL0  4849833.5863  -335048.8133  4116015.0652  0.0000  0.0000  0.0437 AOAD/M_T        NONE
WIND7  5633708.8016  1732017.9297 -2433985.5795  0.0000  0.0000  0.0460 ASH700936C_M    SNOW
WTZR0  4075580.3797   931853.9767  4801568.2360  0.0000  0.0000  0.0710 LEIAR25.R3      LEIT
WUH27 -2267749.9761  5009154.5504  3221294.4429  0.0000  0.0000  0.1206 JAV_RINGANT_G3T NONE
YELL7 -1224452.8796 -2689216.1863  5633638.2832  0.0000  0.0000  0.1000 AOAD/M_T        NONE

Note that the only mandatory parameters in this file are the 'Station' parameters, each standing for an observation stream's mountpoint or the 4-character station ID of a RINEX filename. The following shows further valid examples for records of a 'Coordinates' file.

!
! Station     X[m]         Y[m]          Z[m]    N[m]   E[m]   U[m]  Antenna        Radom
! ---------------------------------------------------------------------------------------
FFMJ1   4053455.7384  617729.8393  4869395.8214  0.000  0.000  0.045
TITZ1   3993780.4501  450206.8969  4936136.9886
WARN
SASS1         0.0          0.0           0.0     0.000  0.000  0.031 TPSCR3_GGD      CONE

In this file

• Record 'FFMJ1' describes a stream from a stationary receiver with known a priori marker coordinate and antenna eccentricity but unknown antenna name and radome.
• Record 'TITZ1' describes a stream coming from a stationary receiver where an a priori marker coordinate is known but antenna eccentricity, name and radome are unknown.
• The 4-character station ID 'WARN' indicates that a RINEX observations file for post processing PPP is available for station 'WARN' but an a priori marker coordinate as well as antenna eccentricity, name and radome are unknown.
• Record 'SASS1' stands for a mountpoint where the stream comes from a mobile rover receiver. Hence an a priori coordinate is unknown although antenna eccentricity, name and radome are known.

First of all, PPP results are shown in the 'Log' tab on the bottom of BNC's main window. Depending on the processing options, the following values are presented about once per second (example):

...
15-07-07 08:33:30 2015-07-07_08:33:45.000 FFMJ1 X = 4053455.7609 Y = 617729.8466 Z = 4869395.8584 NEU:  +0.0059  +0.0038  +0.0434 TRP:  +2.3453  +0.0485
15-07-07 08:33:31 2015-07-07_08:33:47.000 FFMJ1 X = 4053455.7565 Y = 617729.8451 Z = 4869395.8560 NEU:  +0.0078  +0.0030  +0.0386 TRP:  +2.3453  +0.0522
15-07-07 08:33:34 2015-07-07_08:33:49.000 FFMJ1 X = 4053455.7565 Y = 617729.8542 Z = 4869395.8479 NEU:  +0.0015  +0.0120  +0.0332 TRP:  +2.3453  +0.0583
15-07-07 08:33:36 2015-07-07_08:33:51.000 FFMJ1 X = 4053455.7592 Y = 617729.8517 Z = 4869395.8562 NEU:  +0.0051  +0.0091  +0.0411 TRP:  +2.3453  +0.0628
15-07-07 08:33:37 2015-07-07_08:33:53.000 FFMJ1 X = 4053455.7576 Y = 617729.8562 Z = 4869395.8466 NEU:  -0.0004  +0.0138  +0.0331 TRP:  +2.3453  +0.0670
...

Each row reports the PPP result of one epoch. It begins with a UTC time stamp (yy-mm-dd hh:mm:ss) which tells us when the result was produced. A second time stamp (yyyy-mm-dd_hh:mm:ss) describes the PPP's epoch in 'GPS Time'. It is followed by the derived XYZ position in [m], its North, East and Up displacement compared to an introduced a priori coordinate and the estimated tropospheric delay [m] (model plus correction).

If you require more information, you can specify the full path to daily PPP 'Logfile' per PPP solution to save additional processing details on disk. Example:

   /Users/pppDir/PPP_${STATION}_${DATE}.log

In this '${STATION}' stands for the observation's mountpoint or RINEX file and '${DATE}' for the date. For an observation's stream 'FFMJ1' it would lead to a logfile named 'PPP_FFMJ1_2015-07-07.log with the following contents per epoch (example):

Results of Epoch 2015-06-30_10:37:00.000
--------------------------------------
2015-06-30_10:37:00.000 BANCROFT:   -2364339.137    4870286.804   -3360814.597     -24882.876

2015-06-30_10:37:00.000 RES cIF G05   1.5881
2015-06-30_10:37:00.000 RES cIF G07   2.7378
2015-06-30_10:37:00.000 RES cIF G10  -0.7913
2015-06-30_10:37:00.000 RES cIF G13  -0.8838
2015-06-30_10:37:00.000 RES cIF G28  -2.2195
2015-06-30_10:37:00.000 RES cIF G30   1.1955
2015-06-30_10:37:00.000 RES lIF G05  -0.0137
2015-06-30_10:37:00.000 RES lIF G07   0.0069
2015-06-30_10:37:00.000 RES lIF G10   0.0206
2015-06-30_10:37:00.000 RES lIF G13   0.0061
2015-06-30_10:37:00.000 RES lIF G28  -0.0167
2015-06-30_10:37:00.000 RES lIF G30   0.0002
2015-06-30_10:37:00.000 RES lIF R05   0.0114
2015-06-30_10:37:00.000 RES lIF R06   0.0038
2015-06-30_10:37:00.000 RES lIF R07  -0.0169
2015-06-30_10:37:00.000 RES lIF R09   0.0106
2015-06-30_10:37:00.000 RES lIF R16  -0.0109

2015-06-30_10:37:00.000 CLK             0.0000    -2.9038 +-   0.6250
2015-06-30_10:37:00.000 AMB lIF G05  2569.0000   +25.6866 +-   5.6947 el =  44.28 epo =   27
2015-06-30_10:37:00.000 AMB lIF G07   960.0000   +25.4561 +-   5.6987 el =  39.75 epo =   27
2015-06-30_10:37:00.000 AMB lIF G10  1266.0000   +24.7084 +-   5.6950 el =  53.91 epo =   27
2015-06-30_10:37:00.000 AMB lIF G13 -3098.0000   +25.4074 +-   5.8291 el =  22.07 epo =   27
2015-06-30_10:37:00.000 AMB lIF G28  1741.0000   +25.4311 +-   5.6952 el =  54.09 epo =   27
2015-06-30_10:37:00.000 AMB lIF G30  -601.0000   +25.6923 +-   5.6987 el =  65.78 epo =   27
2015-06-30_10:37:00.000 AMB lIF R05  -500.0000    +6.5369 +-  35.3675 el =  30.11 epo =   24
2015-06-30_10:37:00.000 AMB lIF R06  -505.0000    +5.5080 +-  35.3072 el =  87.28 epo =    5
2015-06-30_10:37:00.000 AMB lIF R07  -768.0000    -1.2722 +-  35.4211 el =  34.99 epo =    6
2015-06-30_10:37:00.000 AMB lIF R09   343.0000    -2.1249 +-  35.3255 el =  51.23 epo =   27
2015-06-30_10:37:00.000 AMB lIF R16   -78.0000    -2.0550 +-  35.3383 el =  55.29 epo =   27
2015-06-30_10:37:00.000 OGG            -4.1622    +2.2266 +-   3.7714
2015-06-30_10:37:00.000 TRP             2.4018    -0.0078 +-   0.0997
2015-06-30_10:37:00.000 CUT07 X = -2364337.4403 +- 0.0262 Y = 4870285.6044 +- 0.0403 Z = -3360809.6277 +- 0.0315 dN = -0.0004 +- 0.0200 dE = 0.0000 +- 0.0200 dU = -0.0012 +- 0.0500

Depending on selected processing options you find 'GPS Time' stampes (yyyy-mm-dd_hh:mm:ss.sss) followed by

• RES: Code and phase residuals for contributing GNSS systems in [m]
  Given per satellite with cIF/lIF for ionosphere-free linear combination of code/phase observations
• CLK: Receiver clock errors in [m],
• AMB: L3 biases, also known as 'floated ambiguities'
  Given per satellite with 'el' = satellite elevation angle, 'epo' = number of epochs since last ambiguity reset
• OGG: Time offset between GPS time and Galileo time in [m],
• TRP: A priori and correction values of tropospheric zenith delay in [m],
• MOUNTPOINT: Here 'CUT07' with XYZ position in [m] and dN/dE/dU in [m] for North, East, and Up displacements comparted to a priori marker coordinates.

Default value for 'Logfile' is an empty option field, meaning that you don't want to save daily PPP logfiles on disk.

IGS provides a file containing absolute phase center corrections for GNSS satellite and receiver antennas in ANTEX format. Entering the full path to such an ANTEX file is required for correcting observations in PPP for antenna phase center offsets and variations. Note that for applying such corrections you need to specify the receiver's antenna name and radome in BNC's 'Coordinates' file.

Default value for 'ANTEX file' is an empty option field, meaning that you don't want to correct observations for antenna phase center offsets and variations.

You can specify the full path to daily NMEA files per PPP solution where Point Positioning results are saved as NMEA sentences. Example:

   /Users/pppDir/PPP_${STATION}_${DATE}.nmea

In this '${STATION}' stands for the observation's mountpoint or RINEX file and '${DATE}' for the date. For an observation's stream 'FFMJ1' it would lead to a NMEA file named 'PPP_FFMJ1_2015-07-07.nmea'. Its contents would be NMEA sentences generated about once per second with pairs of

• GPGGA sentences which mainly carry the estimated latitude, longitude, and height values, plus
• GPRMC sentences which mainly carry date and time information.

$GPRMC,112348,A,3200.233,S,11553.688,E,,,300615,,*A
$GPGGA,112348,3200.2332035,S,11553.6880127,E,1,13,1.4,23.971,M,0.0,M,,*5D
$GPRMC,112349,A,3200.233,S,11553.688,E,,,300615,,*B
$GPGGA,112349,3200.2332035,S,11553.6880127,E,1,13,1.4,23.971,M,0.0,M,,*5C
$GPRMC,112350,A,3200.233,S,11553.688,E,,,300615,,*3
$GPGGA,112350,3200.2332035,S,11553.6880127,E,1,13,1.4,23.971,M,0.0,M,,*54
$GPRMC,112351,A,3200.233,S,11553.688,E,,,300615,,*2
$GPGGA,112351,3200.2332035,S,11553.6880127,E,1,13,1.4,23.971,M,0.0,M,,*55
$GPRMC,112352,A,3200.233,S,11553.688,E,,,300615,,*1
$GPGGA,112352,3200.2332035,S,11553.6880127,E,1,13,1.4,23.971,M,0.0,M,,*56
$GPRMC,112353,A,3200.233,S,11553.688,E,,,300615,,*0
$GPGGA,112353,3200.2332035,S,11553.6880127,E,1,13,1.4,23.971,M,0.0,M,,*57
$GPRMC,112354,A,3200.233,S,11553.688,E,,,300615,,*7
$GPGGA,112354,3200.2332035,S,11553.6880127,E,1,13,1.4,23.971,M,0.0,M,,*50
$GPRMC,112355,A,3200.233,S,11553.688,E,,,300615,,*6
$GPGGA,112355,3200.2332035,S,11553.6880127,E,1,13,1.4,23.971,M,0.0,M,,*51
$GPRMC,112356,A,3200.233,S,11553.688,E,,,300615,,*5
$GPGGA,112356,3200.2332035,S,11553.6880127,E,1,13,1.4,23.971,M,0.0,M,,*52
...

The default value for 'NMEA file' is an empty option field, meaning that BNC will not save NMEA messages into a file.

Note that Tomoji Takasu has written a program named RTKPLOT for visualizing NMEA sentences from IP ports or files. It is available from http://www.rtklib.com and compatible with the 'NMEA file' and port output of BNC's 'PPP' client option.

BNC estimates the tropospheric delay according to equation

   T(z) = T_apr(z) + dT / cos(z)

You can specify the full path to daily SINEX Troposphere files to save troposphere parameters on disk, see https://igscb.jpl.nasa.gov/igscb/data/format/sinex_tropo.txt for a documentation of the file format. Example:

   /Users/pppDir/PPP_${STATION}${DOY}_${YY}.zpd

%=TRO 0.01 BNC 15:181:38193 BNC 15:181:38193 15:181:84600 P CUT0
+FILE/REFERENCE
 DESCRIPTION        BNC generated SINEX TRO file
 OUTPUT             Total Troposphere Zenith Path Delay Product
 SOFTWARE           BNC 2.12
 HARDWARE           MAC
 INPUT              Orbit and Clock information used from BRDC and RTCM-SSR streams
-FILE/REFERENCE

+TROP/DESCRIPTION
*KEYWORD______________________ VALUE(S)______________
 SAMPLING INTERVAL                                  1
 SAMPLING TROP                                      1
 ELEVATION CUTOFF ANGLE                            10
 TROP MAPPING FUNCTION         Saastamoinen
 SOLUTION_FIELDS_1             TROTOT STDEV
-TROP/DESCRIPTION

+TROP/STA_COORDINATES
*SITE PT SOLN T STA_X_______ STA_Y_______ STA_Z_______ SYSTEM REMARK
 CUT0  A    1 P -2364337.441  4870285.605 -3360809.628 ITRF08
-TROP/STA_COORDINATES

+TROP/SOLUTION
*SITE EPOCH_______ TROTOT STDEV
 CUT0 15:181:38193    0.0   0.0
 CUT0 15:181:38194 2402.0 100.0
 CUT0 15:181:38195 2402.0 100.0
 CUT0 15:181:38196 2402.1 100.0
 CUT0 15:181:38197 2402.0 100.0
 CUT0 15:181:38198 2401.8 100.0
 CUT0 15:181:38199 2401.6  99.9
 CUT0 15:181:38200 2401.7  99.9
 CUT0 15:181:38201 2401.6  99.9
 CUT0 15:181:38202 2401.5  99.9
 CUT0 15:181:38203 2401.3  99.9
 CUT0 15:181:38204 2401.0  99.9
 CUT0 15:181:38205 2400.8  99.9
 CUT0 15:181:38206 2400.5  99.9
 CUT0 15:181:38207 2400.3  99.9
 CUT0 15:181:38208 2399.8  99.9
 CUT0 15:181:38209 2399.6  99.9
 CUT0 15:181:38210 2399.3  99.9
 CUT0 15:181:38211 2398.9  99.8
 CUT0 15:181:38212 2398.5  99.8
 CUT0 15:181:38213 2397.9  99.8
 CUT0 15:181:38214 2397.3  99.8
 CUT0 15:181:38215 2396.7  99.8
 CUT0 15:181:38216 2396.2  99.8
 CUT0 15:181:38217 2395.6  99.8
 CUT0 15:181:38218 2395.1  99.7
 CUT0 15:181:38219 2394.6  99.7
 CUT0 15:181:38220 2394.0  99.7
 CUT0 15:181:38221 2393.2  99.7
-TROP/SOLUTION
%=ENDTROP

The default value for 'SNX TRO File' is an empty option field, meaning that BNC will not save SINEX Troposphere files.

Select the length of SINEX Troposphere files.

Default 'Interval' for saving SINEX Troposphere files on disk is '1 day'.

Select a 'Sampling' rate in seconds for saving troposphere parameters.

Default 'Sampling' rate is '0', meaning that all troposphere estimates will be save on disk.

This panel allows to enter parameters specific to each PPP process or thread. Individual sigmas for a priori coordinates and a noise for coordinate variations over time can be introduced. Furthermore, a sigma for model based troposphere estimates and the corresponding noise for troposphere variations can be specified. Finally, local IP server ports can be defined for output of NMEA streams carrying PPP results.

BNC offers to create a table with one line per PPP process or thread to specify station-specific parameters. Hit the 'Add Station' button to create a table or add a new line to it. To remove a line from the table, highlight it by clicking it and hit the 'Delete Station' button. You can also remove multiple lines simultaneously by highlighting them using +Shift and +Ctrl.

BNC will simultaneously produce PPP solutions for all stations listed in the 'Station' column of this table.

Figure 23: Precise Point Positioning with BNC, PPP Panel 2.

Hit the 'Add Station' button, double click on the 'Station' field, then specify an observation's mountpoint from the 'Streams' section or introduce the 4-character Station ID of your RINEX observation file and hit Enter. BNC will only produce PPP solutions for stations listed in this table.

Enter a sigmas in meters for the initial coordinate components. A value of 100.0 (default) may be an appropriate choice. However, this value may be significantly smaller (i.e. 0.01) when starting for example from a station with well-known position - so-called Quick-Start mode.

Enter a white 'Noise' in meters for estimated coordinate components. A value of 100.0 (default) may be appropriate when considering possible sudden movements of a rover.

Enter a sigma in meters for the a priori model based tropospheric delay estimation. A value of 0.1 (default) may be an appropriate choice.

Enter a white 'Noise' in meters per second to describe the expected variation of the tropospheric effect. Supposing 1Hz observation data, a value of 3e-6 (default) would mean that the tropospheric effect may vary for 3600 * 3e-6 = 0.01 meters per hour.

Note that Tomoji Takasu has written a program named RTKPLOT for visualizing NMEA sentences from IP ports or files. It is available from http://www.rtklib.com and compatible with the NMEA file and port output of BNC's 'PPP' client option.

Furthermore, NASA's 'World Wind' software (see http://worldwindcentral.com/wiki/NASA_World_Wind_Download) can be used for real-time visualization of positions provided through BNC's NMEA IP output port. You need the 'GPS Tracker' plug-in available from http://worldwindcentral.com/wiki/GPS_Tracker for that. The 'Word Wind' map resolution is not meant for showing centimeter level details.

BNC allows using various Point Positioning processing options depending on the capability of the involved receiver and the application in mind. It also allows introducing specific sigmas for code and phase observations as well as for a priori coordinates and troposphere estimates. You may also like to carry out your PPP solution in Quick-Start mode or enforce BNC to restart a solution if the length of an outage exceeds a certain threshold.

The intention of this panel is to specify general processing options to be applied to all PPP threads in one BNC job.

Figure 24: Precise Point Positioning with BNC, PPP Panel 3.

Specify on which ionosphere-free Linear Combinations (LCs) of observations you want to base ambiguity resolutions. This implicitly defines the kind of GNSS observations you want to use. The specification is to be done per GNSS system ('GPS LCs', 'GLONASS LCs', 'Galileo LCs', 'BDS LCs').

• Selecting 'P3' means that you request BNC to use code data and the so-called P3 ionosphere-free linear combinations of code observations.
• 'L3' means that you request BNC to use phase data and the so-called L3 ionosphere-free linear combinations of phase observations.
• 'P3&L3' means that you request BNC to use both, code and phase data and the so-called P3 and L3 ionosphere-free linear combinations of code and phase observations.

Note that most geodetic GPS receivers support the observation of both, code and phase data. Hence specifying 'P3&L3' would be a good choice for GPS when processing data from such a receiver. If multi-GNSS data processing is your intention, make sure your receiver supports GLONASS and/or Galileo and/or BDS observations besides GPS. Note also that the Broadcast Corrections stream or file which is required for PPP also supports all the systems you have in mind.

Specifying 'no' means that you don't at all want BNC to use observations from the affected GNSS system.

Specify a maximum for residuals 'Max Res C1' for C1 code observations in a PPP solution. '3.0' meters may be an appropriate choice for that. If the maximum is exceeded, contributions from the corresponding observation will be ignored in the PPP solution.

Enter a 'Sigma L1' for L1 phase observations in meters. The bigger the sigma you enter, the less the contribution of L1 phase observations to a PPP solutions based on a combination of code and phase data. '0.01' meters is likely to be an appropriate choice.

Specify a maximum for residuals 'Max Res L1' for L1 phase observations in a PPP solution. '0.03' meters may be an appropriate choice for that. If the maximum is exceeded, contributions from the corresponding observation will be ignored in the PPP solution.

As the convergence characteristic of a PPP solution can be influenced by the ratio of sigmas for code and phase, you may like to introduce sigmas which differ from the default values.

• Introducing a smaller sigma (higher accuracy) for code observations or a bigger sigma for phase observations leads to better results shortly after program start. However, it may take more time till you finally get the best possible solution.
• Introducing a bigger sigma (lower accuracy) for code observations or a smaller sigma for phase observations may lead to less accurate results shortly after program start and thus a prolonged period of convergence but could provide better positions in the long run.

BNC allows elevation dependent weighting when processing GNSS observations. A weight function

      P = cos² * z

with 'z' being the zenith distance to the involved satellite can be applied instead of the simple weight function 'P = 1'.

• Tick 'Ele Wgt Code' if you want Elevation Dependent Weighting for code observations.
• Tick 'Ele Wgt Phase' if you want Elevation Dependent Weighting for phase observations.

Default is using the plain weight function 'P = 1' for code and phase observations.

Select the minimum number of observations you want to use per epoch. The minimum for parameter 'Min # of Obs' is '4'. This is also the default.

Select a minimum for satellite elevation angles. Selecting '10 deg' for option 'Min Elevation' may be an appropriate choice.

Default is '0 deg' meaning that any observation will be used regardless of the involved satellite elevation angle.

Zero value (or 'no') for 'Wait for clock corr.' means that BNC processes each epoch of data immediately after its arrival using satellite clock corrections available at that time. Non-zero value means that epochs of data are buffered and the processing of each epoch is postponed till satellite clock corrections not older than 'Wait for clock corr.' are available. Specifying a value of half the update rate of the clock corrections (i.e. 5 sec) may be appropriate. Note that this causes an additional delay of the PPP solutions in the amount of half of the update rate.

Using observations in sync with the corrections can avoid a possible high frequency noise of PPP solutions. Such noise could result from processing observations regardless of how late after a clock correction they were received. Note that applying the 'Wait for clock corr.' option significantly reduces the PPP computation effort for BNC.

Default is an empty option field, meaning that you want BNC to process observations immediately after their arrival through applying the latest received clock correction.

Enter the length of a startup period in seconds for which you want to fix the PPP solution to an known position, see option 'Coordinates'. Constraining a priori coordinates is done in BNC through setting their white 'Noise' temporarily to zero.

This so-called Quick-Start option allows the PPP solutions to rapidly converge after startup. It requires that the antenna remains unmoved on the known position throughout the defined period. A value of '60' seconds is likely to be an appropriate choice for 'Seeding'. Default is an empty option field, meaning that you don't want BNC to start in Quick-Start mode.

You may need to create your own reference coordinate beforehand through running BNC for an hour in normal mode before applying the 'Seeding' option. Don't forget to introduce realistic North/East/Up sigmas under panel 'PPP (2)' according to the coordinate's precision.

'Seeding' has also a function for bridging gaps in PPP solutions from failures caused i.e. by longer lasting outages. Should the time span between two consecutive solutions exceed the limit of 60 seconds (maximum solution gap, hard-wired), the algorithm fixes the latest derived coordinate for a period of 'Seeding' seconds. This option avoids time-consuming reconvergences and makes especially sense for stationary operated receivers where convergence can be enforced because a good approximation for the receiver position is known.

The following figure provides the screenshot of an example PPP session with BNC.

Figure 25: BNC in 'Quick-Start' mode (PPP, Panel 2)

This panel presents options for visualizing PPP results as a time series plot or as a track map with PPP tracks on top of OSM or Google maps.

PPP time series of North (red), East (green) and Up (blue) displacements will be plotted under the 'PPP Plot' tab when this option is ticked. Values will be either referred to an XYZ reference coordinate (if specified, see 'Coordinates') or referred to the first estimated position. The sliding PPP time series window will cover the period of the latest 5 minutes.

Note that a PPP time series makes only sense for a stationary operated receiver.

For natural hazard prediction and monitoring landslides it may be appropriate to generate audio alerts. For that you can specify an 'Audio response' threshold in meters. A beep is produced by BNC whenever a horizontal PPP coordinate component differs by more than the threshold value from the specified marker coordinate.

Default is an empty option field, meaning that you don't want BNC to produce acoustic warnings.

You may like to track your rover position using Google Maps or OpenStreetMap as a background map. Track maps can be produced with BNC in 'Real-time Streams' mode or in 'RINEX Files' post processing mode with data coming from files.

When in 'RINEX Files' post processing mode you should not forget to go online with your host and specify a proxy under the 'Network' panel if that is operated in front of BNC.

The 'Open Map' button opens a windows showing a map according to the selected 'Google/OSM' option.

Figure 26: Track of positions from BNC with Google Maps in the background.

Select either 'Google' or 'OSM' as the background map for your rover positions.

Figure 27: Example for a background map from Google Maps and OpenStreetMap (OSM).

PPP tracks are presented on maps through plotting one colored dot per observation epoch.

Specify the size of dots showing the rover position. A dot size of '3' may be appropriate. The maximum possible dot size is '10'. An empty option field or a size of '0' would mean that you don't want BNC to show the rover's track on the map.

Select the color of dots showing the rover track.

With BNC in 'RINEX File' post processing mode for PPP you can specify the speed of computations as appropriate for visualization. Note that you can adjust 'Post-processing speed' on-the-fly while BNC is already processing your observations.

BNC allows processing several orbit and clock correction streams in real-time to produce, encode, upload and save a combination of Broadcast Corrections from various providers. All corrections must refer to satellite Antenna Phase Centers (APC). It is so far only the satellite clock corrections which are combined while orbit corrections in the combination product as well as the product update rates are just taken over from one of the incoming Broadcast Correction streams. Combining only clock corrections using a fixed orbit reference has the possibility to introduce some analysis inconsistencies. We may therefore eventually consider improvements on this approach. The clock combination can be based either on a plain 'Single-Epoch' or on a Kalman 'Filter' approach.

In the Kalman Filter approach satellite clocks estimated by individual Analyses Centers (ACs) are used as pseudo observations within the adjustment process. Each observation is modeled as a linear function (actually a simple sum) of three estimated parameters: AC specific offset, satellite specific offset common to all ACs, and the actual satellite clock correction which represents the result of the combination. These three parameter types differ in their statistical properties. The satellite clock offsets are assumed to be static parameters while AC specific and satellite specific offsets are stochastic parameters with appropriate white noise. The solution is regularized by a set of minimal constraints. After a change of one of the three values 'SSR Provider ID', 'SSR Solution ID', or 'IOD SSR', the satellite clock offsets belonging to the corresponding analysis center are reset in the adjustment.

Removing the AC-dependent biases as well as possible is a major issue with clock combinations. Since they vary in time, it can be tricky to do this. Otherwise, there will be artificial jumps in the combined clock stream if one or more AC contributions drop out for certain epochs. Here the Kalman Filter approach is expected to do better than the Single-Epoch approach.

In view of IGS real-time products, the 'Combine Corrections' functionality has been integrated in BNC because

• The software with its Graphic User Interface and wide range of supported Operating Systems represents a perfect platform to process many Broadcast Correction streams in parallel;
• Outages of single AC product streams can be mitigated through merging several incoming streams into a combined product;
• Generating a combination product from several AC products allows detecting and rejecting outliers;
• A Combination Center (CC) can operate BNC to globally disseminate a combination product via Ntrip broadcast;
• An individual AC could prefer to disseminate a stream combined from primary and backup IT resources to reduce outages;
• It enables a BNC PPP user to follow his own preference in combining streams from individual ACs for Precise Point Positioning;
• It allows an instantaneous quality control of the combination process not only in the time domain but also in the space domain; this can be done through direct application of the combined stream in a PPP solution even without prior upload to an Ntrip Broadcaster;
• It provides the means to output SP3 and Clock RINEX files containing precise orbit and clock information for further processing using other tools than BNC.

Note that the combination process requires real-time access to Broadcast Ephemeris. So, in addition to the orbit and clock correction streams BNC must pull a stream carrying Broadcast Ephemeris in the form of RTCM Version 3 messages. Stream 'RTCM3EPH' on caster products.igs-ip.net is an example for that. Note further that BNC will ignore incorrect or outdated Broadcast Ephemeris data when necessary, leaving a note 'WRONG EPHEMERIS' or 'OUTDATED EPHEMERIS' in the logfile.

A combination is carried out following a specified sampling interval. BNC waits for incoming Broadcast Corrections for the period of one such interval. Corrections received later than that will be ignored. If incoming streams have different rates, only epochs that correspond to the sampling interval are used.

With respect to IGS, it is important to understand that a major effect in the combination of GNSS orbit and clock correction streams is the selection of ACs to include. It is likely that a combination product could be improved in accuracy by using only the best two or three ACs. However, with only a few ACs to depend on, the reliability of the combination product could suffer and the risk of total failures increases. So there is an important tradeoff here that must be considered when selecting streams for a combination. The major strength of a combination product is its reliability and stable median performance which can be much better than that of any single AC product.

This comment applies in situations where we have a limited number of solutions to combine and their quality varies significantly. The situation may be different when the total number of ACs is larger and the range of AC variation is smaller. In that case, a standard full combination is probably the best.

The following recursive algorithm is used to detect orbit outliers in the Kalman Filter combination when Broadcast Corrections are provided by several ACs:
Step 1: We don't produce a combination for a certain satellite if only one AC provides corrections for it.
Step 2: A mean satellite position is calculated as the average of positions from all ACs.
Step 3: For each AC and satellite the 3D distance between individual and mean satellite position is calculated.
Step 4: We find the greatest difference between AC specific and mean satellite positions.
Step 5: If that is less than a threshold, the conclusion is that we don't have an outlier and can proceed to the next epoch.
Step 6: If that is greater than a threshold, then corrections of the affiliated AC are ignored for the affected epoch and the outlier detection restarts with step 1.

Note that BNC can produce an internal PPP solution from combined Broadcast Corrections. For that you have to specify the keyword 'INTERNAL' as 'Corrections' mountpoint in the PPP (1) panel.

The part of BNC which enables the combination of Broadcast Corrections is not intended for publication under GNU General Public License (GPL). However, pre-compiled BNC binaries which support the 'Combine Corrections' option are made available.

Hit the 'Add Row' button, double click on the 'Mountpoint' field, enter a Broadcast Corrections mountpoint from the 'Streams' section and hit Enter. Then double click on the 'AC Name' field to enter your choice of an abbreviation for the Analysis Center (AC) providing the Antenna Phase Center (APC) related stream. Finally, double click on the 'Weight' field to enter a weight to be applied to this stream in the combination.

The sequence of entries in the 'Combine Corrections' table is not of importance. Note that the orbit information in the final combination stream is just copied from one of the incoming streams. The stream used for providing the orbits may vary over time: if the orbit providing stream has an outage then BNC switches to the next remaining stream for getting hold of the orbit information.

It is possible to specify only one Broadcast Ephemeris corrections stream in the 'Combine Corrections' table. Instead of combining corrections from several sources, BNC will then merge the single corrections stream with Broadcast Ephemeris to save results in SP3 and/or Clock RINEX format when specified accordingly under the 'Upload Corrections' panel. Note that in such a BNC application you must not pull more than one Broadcast Ephemeris corrections stream even if a second stream would provide the same corrections from a backup caster.

Default is an empty 'Combine Corrections' table meaning that you don't want BNC to combine orbit and clock correction streams.

Hit 'Add Row' button to add another row to the 'Combine Corrections' table or hit the 'Delete' button to delete the highlighted row(s).

The following screenshots describe an example setup of BNC when combining Broadcast Correction streams and uploading them to an Ntrip Broadcaster. Note that this application requires specifying options under panels 'Combine Corrections' and 'Upload Corrections'. The example uses the combination product to simultaneously carry out an 'INTERNAL' PPP solution which allows monitoring the quality of the combination product in the space domain.

Figure 28: BNC combining Broadcast Correction streams.

Figure 29: BNC uploading the combined Broadcast Corrections stream.

Figure 30: 'INTERNAL' PPP with BNC using combined Broadcast Corrections stream.

Select a clock combination method. Available options are Kalman 'Filter' and 'Single-Epoch. It is suggested to use the Kalman Filter approach in case the combined stream of Broadcast Corrections is intended for Precise Point Positioning.

BNC combines all incoming clocks according to specified weights. Individual clock estimates that differ by more than 'Maximal Residuum' meters from the average of all clocks will be ignored.

Default is a 'Maximal Residuum' of 999.0 meters

Specify a combination sampling interval. Orbit and clock corrections will be produced following that interval. A value of 10 sec may be an appropriate choice.

You may tick the 'Use GLONASS' option in case you want to produce a GPS plus GLONASS combination and both systems are supported by the Broadcast Correction streams participating in the combination.

BNC can upload streams carrying orbit and clock corrections to Broadcast Ephemeris in radial, along-track and cross-track components if they are

1. either generated by BNC as a combination of several individual Broadcast Correction streams coming from an number of real-time Analysis Centers (ACs), see section 'Combine Corrections',
2. or generated by BNC while the program receives an ASCII stream of precise satellite orbits and clocks via IP port from a connected real-time GNSS engine. Such a stream would be expected in a plain ASCII format and the associated 'decoder' string would have to be 'RTNET', see format description below.

• Continuously receive up-to-date Broadcast Ephemeris carrying approximate orbits and clocks for all satellites. Read new Broadcast Ephemeris immediately whenever they become available. This information may come via a stream of RTCM messages generated from another BNC instance.

• Continuously receive the best available orbit and clock estimates for all satellites in XYZ Earth-Centered-Earth-Fixed IGS08 reference system. Receive them every epoch in plain ASCII format as provided by a real-time GNSS engine such as RTNET or generate them following a combination approach.
• Calculate XYZ coordinates from Broadcast Ephemeris orbits.
• Calculate differences dX,dY,dZ between Broadcast Ephemeris and IGS08 orbits.
• Transform these differences into radial, along-track and cross-track corrections to Broadcast Ephemeris orbits.
• Calculate corrections to Broadcast Ephemeris clocks as differences between Broadcast Ephemeris clocks and IGS08 clocks.
• Encode Broadcast Ephemeris orbit and clock corrections in RTCM Version 3 format.
• Upload Broadcast Corrections stream to Ntrip Broadcaster.

The orbit and clock corrections to Broadcast Ephemeris are usually referred to the latest set of broadcast messages, which are generally also received in real-time by a GNSS rover. However, the use of the latest broadcast message is delayed for a period of 60 seconds, measured from the time of complete reception of ephemeris and clock parameters, in order to accommodate rover applications to obtain the same set of broadcast orbital and clock parameters. This procedure is recommended in the RTCM SSR standard.

The usual handling of BNC when uploading a stream with Broadcast Corrections is that you first specify Broadcast Ephemeris and Broadcast Correction streams. You then specify an Ntrip Broadcaster for stream upload before you start the program.

'RTNET' Stream Format
When uploading an SSR stream generated according to b. then BNC requires precise GNSS orbits and clocks in the IGS Earth-Centered-Earth-Fixed (ECEF) reference system and in a specific ASCII format named 'RTNET' because the data may come from a real-time engine such as RTNET. The sampling interval for data transmission should not exceed 15 sec. Note that otherwise tools involved in IP streaming such as Ntrip Broadcasters or Ntrip Clients may respond with a timeout.

Below you find an example for the 'RTNET' ASCII format coming from a real-time GNSS engine. Each epoch begins with an asterisk character followed by the time as year, month, day of month, hour, minute and second. Subsequent records can provide

A set of parameters can be defined for each satellite as follows:

<SatelliteID> <key> <numValues> <value1 value2 ...> <key> <numValues> <value1 value2 ...> ...  

The following satellite specific keys and values are currently specified in BNC:

Key	Values
APC	Satellite Antenna Phase Center coordinates in meters
Clk	Satellite clock correction in meters, relativistic correction applied like in broadcast clocks
Vel	Satellite velocity in meters per second
CoM	Satellite Center of Mass coordinates in meters
CodeBias	Satellite Code Biases in meters with two characters for frequency and tracking mode per bias as defined in RINEX 3 and preceded by total number of biases
YawAngle	Satellite Yaw Angle in radian, restricted to be in [0, 2π], which shall be used for the computation of phase wind-up correction
YawRate	Satellite Yaw Rate in radian per second, which is the rate of Yaw Angle
PhaseBias	Satellite Phase Biases in meters with two characters for frequency and tracking mode per bias as defined in RINEX 3, preceded by total number of biases and followed by Signal Wilde-Lane Integer Indicator as well as Signal Discontinuity Counter

Button 'Map' opens a window to show a distribution map of the caster's streams. You may like to zoom in or out using the mouse. Left button: draw a rectangle to zoom, right button: zoom out, middle button: zoom back.

Figure 40: Stream distribution map derived from Ntrip Broadcaster source-table.

Button 'Add Stream' > 'Coming from TCP/IP Port' allows to retrieve streams via TCP directly from an IP address without using the Ntrip transport protocol. For that you:

• Enter the IP address of the stream providing host.
• Enter the IP port number of the stream providing host.
• Specify a mountpoint. Recommended is a 4-character station ID. Example: FFMJ
• Specify the stream format. Available options are 'RTCM_2', 'RTCM_3', 'RTNET', and 'ZERO'.
• Enter the approximate latitude of the stream providing rover in degrees. Example: 45.32.
• Enter the approximate longitude of the stream providing rover in degrees. Example: -15.20.

Streams directly received from a TCP/IP port show up with an 'N' for 'No Ntrip' in the 'Streams' canvas on BNC's main window. Latitude and longitude are to be entered just for informal reasons.

Button 'Add Stream' > 'Coming from UDP Port' allows to pick up streams arriving directly at one of the local host's UDP ports without using the Ntrip transport protocol. For that you:

• Enter the local port number where the UDP stream arrives.
• Specify a mountpoint. Recommended is a 4-character station ID. Example: FFMJ
• Specify the stream format. Available options are 'RTCM_2', 'RTCM_3', 'RTNET', and 'ZERO'.
• Enter the approximate latitude of the stream providing rover in degrees. Example: 45.32.
• Enter the approximate longitude of the stream providing rover in degrees. Example: -15.20.

Streams directly received at a UDP port show up with a 'UN' for 'UDP, No Ntrip' in the 'Streams' canvas section on BNC's main window. Latitude and longitude are to be entered just for informal reasons.

Button 'Add Stream' > 'Coming from Serial Port' allows to retrieve streams from a GNSS receiver via serial port without using the Ntrip transport protocol. For that you:

• Specify a mountpoint. Recommended is a 4-character station ID. Example: FFMJ
• Specify the stream format. Available options are 'RTCM_2', 'RTCM_3', 'RTNET', and 'ZERO'.
• Enter the approximate latitude of the stream providing receiver in degrees. Example: 45.32.
• Enter the approximate longitude of the stream providing receiver in degrees. Example: -15.20.
• Enter the serial 'Port name' selected on your host for communication with the receiver. Valid port names are

  Windows:       COM1, COM2
  Linux:         /dev/ttyS0, /dev/ttyS1
  FreeBSD:       /dev/ttyd0, /dev/ttyd1
  Digital Unix:  /dev/tty01, /dev/tty02
  HP-UX:         /dev/tty1p0, /dev/tty2p0
  SGI/IRIX:      /dev/ttyf1, /dev/ttyf2
  SunOS/Solaris: /dev/ttya, /dev/ttyb
  

• Select a 'Baud rate' for the serial input. Note that using a high baud rate is recommended.
• Select the number of 'Data bits' for the serial input. Note that often '8' data bits are used.
• Select the 'Parity' for the serial input. Note that parity is often set to 'NONE'.
• Select the number of 'Stop bits' for the serial input. Note that often '1' stop bit is used.
• Select a 'Flow control' for the serial link. Select 'OFF' if you don't know better.

When selecting one of the serial communication options listed above, make sure that you pick those configured to the serial connected GNSS receiver.

Streams received from a serial connected GNSS receiver show up with an 'S' (for Serial Port, no Ntrip) in the 'Streams' canvas section on BNC's main window. Latitude and longitude are to be entered just for informal reasons.

The following figure shows a BNC example setup for pulling a stream via serial port on a Linux operating system.

Figure 41: BNC setup for pulling a stream via serial port.

Button 'Delete Stream' allows you to delete streams previously selected for retrieval as listed under the 'Streams' canvas on BNC's main window.

Button 'Map' opens a window to show a distribution map of the streams selected for retrieval as listed under the 'Streams' canvas. You may like to zoom in or out using the mouse. Left button: draw a rectangle to zoom, right button: zoom out, middle button: zoom back.

Hit 'Start' to start retrieving, decoding or converting GNSS data streams in real-time. Note that 'Start' generally forces BNC to begin with fresh RINEX which might overwrite existing files when necessary unless the option 'Append files' is ticked.

Hit the 'Stop' button in order to stop BNC.

Command line options are available to run BNC in 'no window' mode or let it read previously recorded input offline from one or several files for debugging purposes. It is also possible to introduce a specific configuration filename instead of using the default filename 'BNC.bnc'. The self-explaining contents of the configuration file can easily be edited.

In addition to reading processing options from the involved configuration file, BNC can optionally read any configuration option from command line. Running BNC with command line option 'help'

Example:

      bnc.exe --help

provides a list of all available command line options.

Command line option '--version' lets BNC print its version number.

Example:

      bnc.exe --version

On systems which support graphics command line option '--display' forces BNC to present the BNC window on the specified display.

Example:

      bnc.exe --display localhost:10.0

Apart from its regular windows mode, BNC can be started on all systems as a batch job with command line option '-nw'. BNC will then run in 'no window' mode, using processing options from its configuration file on disk. Terminate BNC using Windows Task Manager when running it in 'no window' mode on Windows systems.

Example:

      bnc.exe --nw

It is obvious that BNC requires graphics support when started in interactive mode. But, note that it also requires graphics support when producing plots in batch mode (option -nw). Windows and Mac OS X systems always support graphics. For producing plots in batch mode on Linux systems you must make sure that at least a virtual X-Server such as 'Xvfb' is installed and the '-display' option is used. The following is an example shell script to execute BNC in batch mode for producing QC plots from RINEX files. It could be used via 'crontab':

   #!/bin/bash

   # Save string localhost
   echo "localhost" > /home/user/hosts

   # Start virtual X-Server, save process ID
   /usr/bin/Xvfb :29 -auth /home/user/hosts -screen 0 1280x1024x8 &
   psID=`echo $!`

   # Run BNC application with defined display variable
   /home/user/BNC/bnc --conf /dev/null --key reqcAction Analyze --key reqcObsFile ons12090.12o --key reqcNavFile brdc2090.12p --key reqcOutLogFile multi.txt --key reqcPlotDir /home/user --display localhost:29 --nw

   # BNC done, kill X-server process
   kill $psID

Although BNC is primarily a real-time online tool, for debugging purposes it can be run offline to read data from a file previously saved through option 'Raw output file'. Enter the following command line option for that

      --file <inputFileName>

Note that when running BNC offline, it will use options for file saving, interval, sampling, PPP etc. from its configuration file.

Note further that option '--file' forces BNC to apply the '-nw' option for running in 'no window' mode.

Example:

      ./bnc --conf MyConfig.bnc

This leads to a BNC job using configuration file 'MyConfig.bnc'. The configuration file will be saved in the current working directory.

BNC applies options from the configuration file but allows updating every one of them on the command line while the contents of the configuration file remains unchanged. The command line syntax for that looks as follows

      --key <keyName> <keyValue>

where <keyName> stands for the name of an option contained in the configuration file and <keyValue> stands for the value you want to assign to it. The following is a syntax example for a complete command line:

      bnc --nw --conf <confFileName> --key <keyName1> <keyValue1> --key <keyName2> <keyValue2> ...

Configuration options which are part of the configuration files PPP section must be prefixed by 'PPP/'. As an example, option 'minObs' from the PPP section of the BNC configuration file would be specified as 'PPP/minObs' on a command line.

Values for configuration options can be introduced via command line exactly as they show up in the configuration file. However, any value containing one or more blank characters must be enclosed by quotation marks when specified on the command line.

Example command lines:

      (1)   /Applications/bnc.app/Contents/MacOS/bnc -- version
      (2)   ./bnc --conf CONFIG.bnc --key proxyPort 8001 --key rnxIntr "1 day"
      (3)   D:\BKG\bnc.exe --conf C:\Users\weber\Desktop\BNC.bnc --file C:\Users\weber\Desktop\rawfile
      (4)   /home/weber/bin/bnc --conf /home/weber/MyConfigFile.bnc
      (5)   bnc --conf /Users/weber/.config/BKG/BNC.bnc -nw
      (6)   bnc --conf /dev/null --key startTab 4 --key reqcAction Edit/Concatenate --key reqcObsFile AGAR.15O --key reqcOutObsFile AGAR_X.15O --key reqcRnxVersion 2 --key reqcSampling 30 --key reqcV2Priority CWPX_?
      (7)   bnc --key mountPoints "//user:pass@mgex.igs-ip.net:2101/CUT07 RTCM_3.0 ETH 9.03 38.74 no 2;//user:pass@www.igs-ip.net:2101/FFMJ1 RTCM_3.1 DEU 50.09 8.66 no 2"
      (8)   bnc --key cmbStreams "CLK11 BKG 1.0;CLK93 CNES 1.0"
      (9)   bnc --key PPP/staTable "FFMJ1,100.0,100.0,100.0,100.0,100.0,100.0,0.1,3e-6,7777;CUT07,100.0,100.0,100.0,100.0,100.0,100.0,0.1,3e-6,7778"

The Radio Technical Commission for Maritime Services (RTCM) is an international non-profit scientific, professional and educational organization. Special Committees provide a forum in which governmental and non-governmental members work together to develop technical standards and consensus recommendations in regard to issues of particular concern. RTCM is engaged in the development of international standards for maritime radionavigation and radiocommunication systems. The output documents and reports prepared by RTCM Committees are published as RTCM Recommended Standards. Topics concerning Differential Global Navigation Satellite Systems (DGNSS) are handled by the Special Committee SC 104.

Personal copies of RTCM Recommended Standards can be ordered through http://www.rtcm.org/orderinfo.php.

'Networked Transport of RTCM via Internet Protocol' Version 1.0 (Ntrip) stands for an application-level protocol streaming Global Navigation Satellite System (GNSS) data over the Internet. Ntrip is a generic, stateless protocol based on the Hypertext Transfer Protocol HTTP/1.1. The HTTP objects are enhanced to GNSS data streams.

Ntrip Version 1 is an RTCM standard designed for disseminating differential correction data (e.g. in the RTCM-104 format) or other kinds of GNSS streaming data to stationary or mobile users over the Internet, allowing simultaneous PC, Laptop, PDA, or receiver connections to a broadcasting host. Ntrip supports wireless Internet access through Mobile IP Networks like GSM, GPRS, EDGE, or UMTS.

Ntrip is implemented in three system software components: Ntrip Clients, Ntrip Servers and Ntrip Broadcasters. The Ntrip Broadcaster is the actual HTTP server program whereas Ntrip Client and Ntrip Server are acting as HTTP clients.

Ntrip is an open none-proprietary protocol. Major characteristics of Ntrip's dissemination technique are:

• Based on the popular HTTP streaming standard; comparatively easy to implement when having limited client and server platform resources available;
• Application not limited to one particular plain or coded stream content; ability to distribute any kind of GNSS data;
• Potential to support mass usage; disseminating hundreds of streams simultaneously for thousands of users possible when applying modified Internet Radio broadcasting software;
• Considering security needs; stream providers and users don't necessarily get into contact, streams often not blocked by firewalls or proxy servers protecting Local Area Networks;
• Enables streaming over mobile IP networks because of using TCP/IP.

The Ntrip Broadcaster maintains a source-table containing information on available Ntrip streams, networks of Ntrip streams and Ntrip Broadcasters. The source-table is sent to an Ntrip Client on request. Source-table records are dedicated to one of the following: Data Streams (record type STR), Casters (record type CAS), or Networks of streams (record type NET).

Source-table records of type STR contain the following data fields: 'mountpoint', 'identifier', 'format', 'format-details', 'carrier', 'nav-system', 'network', 'country', 'latitude', 'longitude', 'nmea', 'solution', 'generator', 'compr-encryp', 'authentication', 'fee', 'bitrate', 'misc'.

Source-table records of type NET contain the following data fields: 'identifier', 'operator', 'authentication', 'fee', 'web-net', 'web-str', 'web-reg', 'misc'.

Source-table records of type CAS contain the following data fields: 'host', 'port', 'identifier', 'operator', 'nmea', 'country', 'latitude', 'longitude', 'misc'.

The major changes of Ntrip Version 2 compared to Version 1.0 are:

• Cleared and fixed design problems and HTTP protocol violations;
• Replaced non standard directives;
• Chunked transfer encoding;
• Improvements in header records;
• Source-table filtering;
• RTSP communication.

Ntrip Version 2 allows to either communicating in TCP/IP mode or in RTSP/RTP mode or in UDP mode whereas Version 1 is limited to TCP/IP only. It furthermore allows using the Transport Layer Security (TLS) and its predecessor, Secure Sockets Layer (SSL) cryptographic protocols for secure Ntrip communication over the Internet.

Transmitting GNSS carrier phase data can be done through RTCM Version 2 messages. Please note that only RTCM Version 2.2 and 2.3 streams may include GLONASS data. Messages that may be of interest here are:

• Type 1 message is the range correction message and is the primary message in code-phase differential positioning (DGPS). It is computed in the base receiver by computing the error in the range measurement for each tracked SV.
• Type 2 message is automatically generated when a new set of satellite ephemeris is downloaded to the base receiver. It is the computed difference between the old ephemeris and the new ephemeris. Type 2 messages are used when the base station is transmitting Type 1 messages.
• Type 3 and 22 messages are the base station position and the antenna offset. Type 3 and 22 are used in RTK processing to perform antenna reduction.
• Type 6 message is a null frame filler message that is provided for data links that require continuous transmission of data, even if there are no corrections to send. As many Type 6 messages are sent as required to fill in the gap between two correction messages (type 1). Message 6 is not sent in burst mode.
• Type 9 message serves the same purpose as Type 1, but does not require a complete satellite set. As a result, Type 9 messages require a more stable clock than a station transmitting Type 1 's, because the satellite corrections have different time references.
• Type 16 message is simply a text message entered by the user that is transmitted from the base station to the rover. It is used with code-phase differential.
• Type 18 and 20 messages are RTK uncorrected carrier phase data and carrier phase corrections.
• Type 19 and 21 messages are the uncorrected pseudo-range measurements and pseudo-range corrections used in RTK.
• Type 23 message provides the information on the antenna type used on the reference station.
• Type 24 message carries the coordinates of the installed antenna's ARP in the GNSS coordinate system coordinates.

RTCM Version 3 has been developed as a more efficient alternative to RTCM Version 2. Service providers and vendors have asked for a standard that would be more efficient, easy to use, and more easily adaptable to new situations. The main complaint was that the Version 2 parity scheme was wasteful of bandwidth. Another complaint was that the parity is not independent from word to word. Still another was that even with so many bits devoted to parity, the actual integrity of the message was not as high as it should be. Plus, 30-bit words are awkward to handle. The Version 3 standard is intended to correct these weaknesses.

RTCM Version 3 defines a number of message types. Messages that may be of interest here are:

• Type 1001, GPS L1 code and phase.
• Type 1002, GPS L1 code and phase and ambiguities and carrier-to-noise ratio.
• Type 1003, GPS L1 and L2 code and phase.
• Type 1004, GPS L1 and L2 code and phase and ambiguities and carrier-to-noise ratio.
• Type 1005, Station coordinates XYZ for antenna reference point.
• Type 1006, Station coordinates XYZ for antenna reference point and antenna height.
• Type 1007, Antenna descriptor and ID.
• Type 1008, Antenna serial number.
• Type 1009, GLONASS L1 code and phase.
• Type 1010, GLONASS L1 code and phase and ambiguities and carrier-to-noise ratio.
• Type 1011, GLONASS L1 and L2 code and phase.
• Type 1012, GLONASS L1 and L2 code and phase and ambiguities and carrier-to-noise ratio.
• Type 1013, Modified Julian Date, leap second, configured message types and interval.
• Type 1014 and 1017, Network RTK (MAK) messages.
• Type 1019, GPS ephemeris.
• Type 1020, GLONASS ephemeris.
• Type 1043, SBAS ephemeris.
• Type 1044, QZSS ephemeris.
• Type 1045, Galileo F/NAV ephemeris.
• Type 1046, Galileo I/NAV ephemeris.
• Type 63, BeiDou ephemeris, tentative.
• Type 4088 and 4095, Proprietary messages.

The following are so-called 'State Space Representation' (SSR) messages:

• Type 1057, GPS orbit corrections to Broadcast Ephemeris
• Type 1058, GPS clock corrections to Broadcast Ephemeris
• Type 1059, GPS code biases
• Type 1060, Combined orbit and clock corrections to GPS Broadcast Ephemeris
• Type 1061, GPS User Range Accuracy (URA)
• Type 1062, High-rate GPS clock corrections to Broadcast Ephemeris
  
  
• Type 1063, GLONASS orbit corrections to Broadcast Ephemeris
• Type 1064, GLONASS clock corrections to Broadcast Ephemeris
• Type 1065, GLONASS code biases
• Type 1066, Combined orbit and clock corrections to GLONASS Broadcast Ephemeris
• Type 1067, GLONASS User Range Accuracy (URA)
• Type 1068, High-rate GLONASS clock corrections to Broadcast Ephemeris
  
  
• Type 1240, Galileo orbit corrections to Broadcast Ephemeris
• Type 1241, Galileo clock corrections to Broadcast Ephemeris
• Type 1242, Galileo code biases
• Type 1243, Combined orbit and clock corrections to Galileo Broadcast Ephemeris
• Type 1244, Galileo User Range Accuracy (URA)
• Type 1245, High-rate Galileo clock corrections to Broadcast Ephemeris
  
  
• Type 1246, QZSS orbit corrections to Broadcast Ephemeris
• Type 1247, QZSS clock corrections to Broadcast Ephemeris
• Type 1248, QZSS code biases
• Type 1249, Combined orbit and clock corrections to QZSS Broadcast Ephemeris
• Type 1250, QZSS User Range Accuracy (URA)
• Type 1251, High-rate QZSS clock corrections to Broadcast Ephemeris
  
  
• Type 1252, SBAS orbit corrections to Broadcast Ephemeris
• Type 1253, SBAS clock corrections to Broadcast Ephemeris
• Type 1254, SBAS code biases
• Type 1255, Combined orbit and clock corrections to SBAS Broadcast Ephemeris
• Type 1256, SBAS User Range Accuracy (URA)
• Type 1257, High-rate SBAS clock corrections to Broadcast Ephemeris
  
  
• Type 1258, BDS orbit corrections to Broadcast Ephemeris
• Type 1259, BDS clock corrections to Broadcast Ephemeris
• Type 1260, BDS code biases
• Type 1261, Combined orbit and clock corrections to BDS Broadcast Ephemeris
• Type 1262, BDS User Range Accuracy (URA)
• Type 1263, High-rate BDS clock corrections to Broadcast Ephemeris
  
  
• Type 1264 SSR Ionosphere VTEC Spherical Harmonics
• Type 1265 SSR GPS Satellite Phase Bias
• Type 1266 SSR Satellite GLONASS Phase Bias
• Type 1267 SSR Satellite Galileo Phase Bias
• Type 1268 SSR Satellite QZSS Phase Bias
• Type 1269 SSR Satellite SBAS Phase Bias
• Type 1270 SSR Satellite BDS Phase Bias

The following are so-called 'Multiple Signal Messages' (MSM):

• Type 1071, Compact GPS pseudo-ranges
• Type 1072, Compact GPS carrier phases
• Type 1073, Compact GPS pseudo-ranges and carrier phases
• Type 1074, Full GPS pseudo-ranges and carrier phases plus signal strength
• Type 1075, Full GPS pseudo-ranges, carrier phases, Doppler and signal strength
• Type 1076, Full GPS pseudo-ranges and carrier phases plus signal strength (high resolution)
• Type 1077, Full GPS pseudo-ranges, carrier phases, Doppler and signal strength (high resolution)
  
  
• Type 1081, Compact GLONASS pseudo-ranges
• Type 1082, Compact GLONASS carrier phases
• Type 1083, Compact GLONASS pseudo-ranges and carrier phases
• Type 1084, Full GLONASS pseudo-ranges and carrier phases plus signal strength
• Type 1085, Full GLONASS pseudo-ranges, carrier phases, Doppler and signal strength
• Type 1086, Full GLONASS pseudo-ranges and carrier phases plus signal strength (high resolution)
• Type 1087, Full GLONASS pseudo-ranges, carrier phases, Doppler and signal strength (high resolution)
  
  
• Type 1091, Compact Galileo pseudo-ranges
• Type 1092, Compact Galileo carrier phases
• Type 1093, Compact Galileo pseudo-ranges and carrier phases
• Type 1094, Full Galileo pseudo-ranges and carrier phases plus signal strength
• Type 1095, Full Galileo pseudo-ranges, carrier phases, Doppler and signal strength
• Type 1096, Full Galileo pseudo-ranges and carrier phases plus signal strength (high resolution)
• Type 1097, Full Galileo pseudo-ranges, carrier phases, Doppler and signal strength (high resolution)
  
  
• Type 1121, Compact BeiDou pseudo-ranges
• Type 1122, Compact BeiDou carrier phases
• Type 1123, Compact BeiDou pseudo-ranges and carrier phases
• Type 1124, Full BeiDou pseudo-ranges and carrier phases plus signal strength
• Type 1125, Full BeiDou pseudo-ranges, carrier phases, Doppler and signal strength
• Type 1126, Full BeiDou pseudo-ranges and carrier phases plus signal strength (high resolution)
• Type 1127, Full BeiDou pseudo-ranges, carrier phases, Doppler and signal strength (high resolution)
  
  
• Type 1111, Compact QZSS pseudo-ranges
• Type 1112, Compact QZSS carrier phases
• Type 1113, Compact QZSS pseudo-ranges and carrier phases
• Type 1114, Full QZSS pseudo-ranges and carrier phases plus signal strength
• Type 1115, Full QZSS pseudo-ranges, carrier phases, Doppler and signal strength
• Type 1116, Full QZSS pseudo-ranges and carrier phases plus signal strength (high resolution)
• Type 1117, Full QZSS pseudo-ranges, carrier phases, Doppler and signal strength (high resolution)
  
  

The following are proposed 'Multiple Signal Messages' (MSM) under discussion for standardization:

• Type 1101, Compact SBAS pseudo-ranges
• Type 1102, Compact SBAS carrier phases
• Type 1103, Compact SBAS pseudo-ranges and carrier phases
• Type 1104, Full SBAS pseudo-ranges and carrier phases plus signal strength
• Type 1105, Full SBAS pseudo-ranges, carrier phases, Doppler and signal strength
• Type 1106, Full SBAS pseudo-ranges and carrier phases plus signal strength (high resolution)
• Type 1107, Full SBAS pseudo-ranges, carrier phases, Doppler and signal strength (high resolution)
  
  

The following table shows a list of options contained in BNC's configuration files (default filename: BNC.bnc).

Table 2: BNC configuration options

Internal	Meaning
startTab	Top panel index
statusTab	Bottom panel index
font	Used font
casterUrlList	Visited URLs
Network Panel	Meaning
proxyHost	Proxy host
proxyPort	Proxy port
sslCaCertPath	Path to SSL certificates
ignoreSslErrors	Ignore ssl authorization errors
General Panel	Meaning
logFile	Logfile (full path)
rnxAppend	Append files
onTheFlyInterval	Reread configuration
autoStart	Auto start
rawOutFile	Raw output file (full path)
RINEX Observations Panel	Meaning
rnxPath	Directory
rnxIntr	Interval
rnxSample	Sampling
rnxSkel	Skeleton extension
rnxOnlyWithSKL	Skeleton is mandatory
rnxScript	Upload script
rnxV2Priority	Signal priority
rnxV3	Version 3
rnxV3filenames	Version 3 filenames
RINEX Ephemeris Panel	Meaning
ephPath	Directory
ephIntr	Interval
ephOutPort	Port
ephV3	Version 3
ephV3filenames	Version 3 filenames
RINEX Editing and QC Panel	Meaning
reqcAction	Action
reqcObsFile	Input observations file
reqcNavFile	Input navigation file
reqcOutObsFile	Output observations file
reqcOutNavFile	Output navigation file
reqcOutLogFile	Output logfile
reqcLogSummaryOnly	Summary output logfile
reqcSkyPlotSignals	Plots for signals
reqcPlotDir	QC plots directory
reqcRnxVersion	RINEX version
reqcSampling	RINEX sampling
reqcV2Priority	Version 2 signal priority
reqcStartDateTime	Start time
reqcEndDateTime	Stop time
reqcRunBy	Operators name
reqcUseObsTypes	Use observation types
reqcComment	Additional comments
reqcOldMarkerName	Old marker name
reqcNewMarkerName	New marker name
reqcOldAntennaName	Old antenna name
reqcNewAntennaName	New antenna name
reqcOldAntennaNumber	Old antenna number
reqcNewAntennaNumber	New antenna number
reqcOldAntennadN	Old north eccentritity
reqcNewAntennadN	New north eccentricity
reqcOldAntennadE	Old east eccentricity
reqcNewAntennadE	New east eccentricity
reqcOldAntennadU	Old up eccentritity
reqcNewAntennadU	New up eccentricity
reqcOldReceiverName	Old receiver name
reqcNewReceiverName	New receiver name
reqcOldReceiverNumber	Old receiver number
reqcNewReceiverNumber	New receiver number
SP3 Comparison Panel	Meaning
sp3CompFile	SP3 input files
sp3CompExclude	Satellite exclusion list
sp3CompOutLogFile	Output logfile
Broadcast Corrections Panel	Meaning
corrPath	Directory, ASCII
corrIntr	Interval
corrPort	Port
Feed Engine Panel	Meaning
outPort	Port
outWait	Wait for full obs epoch
outSampl	Sampling
outFile	File (full path)
outUPort	Port (unsynchronized)
Serial Output Panel	Meaning
serialMountPoint	Mountpoint
serialPortName	Port name
serialBaudRate	Baud rate
serialFlowControl	Flow control
serialDataBits	Data bits
serialParity	Parity
serialStopBits	Stop bits
serialAutoNMEA	NMEA
serialFileNMEA	NMEA filename
serialHeightNMEA	Height
serialHeightSampling	Sampling
Outages Panel	Meaning
adviseObsRate	Observation rate
adviseFail	Failure threshold
adviseReco	Recovery threshold
adviseScript	Script (full path)
Miscellaneous	Meaning
miscMount	Mountpoint
miscIntr	Log latency
miscScanRTCM	Scan RTCM
miscPort	Port, output
PPP Client Panel 1	Meaning
dataSource	Switch between real-time and post processing
rinexObs	RINEX observation file
rinexNav	RINEX navigation file
corrMount	Corrections mountpoint
corrFile	Corrections file
crdFile	Coordinates file
logFilePPP	PPP logfile
antexFile	ANTEX file
nmeaFile	NMEA output file
snxtroFile	SINEX troposphere output filename
snxtroIntr	SINEX troposphere file interval
snxtroSampl	SINEX troposphere sampling rate
PPP Client Panel 2	Meaning
staTable	Stations table
PPP Client Panel 3	Meaning
lcGPS	Linear combination from GPS code data
lcGLONASS	Linear combination from GLONASS code data
lcGalileo	Linear combination from Galileo code data
lcBDS	Linear combination from BDS code data
sigmaC1	Sigma for code observations
sigmaL1	Sigma for phase observations
maxResC1	Maximal residuum for code observations
maxResL1	Maximal residuum for phase observations
eleWgtCode	Elevation dependent waiting of code observations
eleWgtPhase	Elevation dependent waiting of phase observations
minObs	Minimum number of observations
minEle	Minimum elevation
corrWaitTime	Wait for clock corrections
seedingTime	Seeding time span for Quick Start
PPP Client Panel 4	Meaning
plotCoordinates	Mountpoint for time series plot
audioResponse	Audio response
useOpenStreetMap	OSM track map
useGoogleMap	Google track map
mapWinDotSize	Size of dots on map
mapWinDotColor	Color of dots and cross hair on map
mapSpeedSlider	Offline processing speed for mapping
Combine Corrections Panel	Meaning
combineStreams	Table of correction streams
cmbMethodFilter	Approach
cmbMaxres	Clock outlier threshold
cmbSampl	Orbit and clock sampling
cmbUseGlonass	Use GLONASS in combination
Upload Corrections Panel	Meaning
uploadMountpointsOut	Upload corrections table
uploadIntr	File interval
uploadSamplRtcmEphCorr	Orbit sampling
uploadSamplSp3	Orbit sampling
uploadSamplClkRnx	Clock sampling
Custom Trafo	Meaning
trafo_dx	Translation X
trafo_dy	Translation Y
trafo_dz	Translation Z
trafo_dxr	Translation change X
trafo_dyr	Translation change Y
trafo_dzr	Translation change Z
trafo_ox	Rotation X
trafo_oy	Rotation Y
trafo_oz	Rotation Z
trafo_oxr	Rotation change X
trafo_oyr	Rotation change Y
trafo_ozr	Rotation change Z
trafo_sc	Scale
trafo_scr	Scale change
trafo_t0	Reference year
Upload Ephemeris Panel	Meaning
uploadEphHost	Host
uploadEphPort	Port
uploadEphMountpoint	Mountpoint
uploadEphPassword	Password
uploadEphSample	Sampling
Add Stream	Meaning
mountPoints	Mountpoints list
ntripVersion	Ntrip Version