The BKG Ntrip Client (BNC) is a program for simultaneously retrieving, decoding and converting real-time GNSS data streams from NTRIP broadcasters like http://www.euref-ip.net/home or http://www.igs-ip.net/home.
BNC has been developed for the Federal Agency for Cartography and Geodesy (BKG) within the framework of EUREF's Real-time GNSS Project (EUREF-IP, IP for Internet Protocol) and the Real-Time IGS Pilot Project (RTIGS).
BNC has been written under GNU General Public License (GPL). Binaries for BNC are available for Windows, 32-bit Linux, 64-bit Linux (compiled using option -m32), Solaris, and Mac systems. We used the MinGW Version 5.3.1 compiler to create the Windows binary. It is likely that BNC can be compiled on other systems where a GNU compiler and Qt Version 4.3.2 are installed.
Please ensure that you have installed the latest version of BNC available from http://igs.bkg.bund.de/index_ntrip_down.htm. We are continuously working on the program and would appreciate if you could send any comments, suggestions, or bug reports to [euref-ip@bkg.bund.de] or [igs-ip@bkg.bund.de].
The purpose of BNC is to
BNC supports the following GNSS data formats:
Although BNC is a real-time tool to be operated in online mode, it can be run offline for post processing of data made availabe from a file. Furthermore, apart from its regular window mode, BNC can be run as a batch/background job in a 'no window' mode using processing options from previously saved configuration.
Unless in offline mode, BNC
All options for running BNC on Unix/Linux/Mac systems are saved in file ${HOME}/.config/BKG/BKG_NTRIP_Client.conf, see annexed 'Configuration File' example. On Windows systems options are saved in register BKG_NTRIP_Client. The self-explaining contents of the configuration file or the Windows register can easily be edited. Some options can be changed on-the-fly.
3.1. File
3.2. Help
3.3. Proxy
3.4. General
3.4.1. Logfile
3.4.2. Append Files
3.4.3. Reread Configuration
3.5. RINEX - Observations
3.5.1. File Names
3.5.2. Directory
3.5.3. File Interval
3.5.4. Sampling
3.5.5. Skeleton Extension
3.5.6. Script
3.5.7. Version
3.6. RINEX - Ephemeris
3.6.1. Directory
3.6.2. Interval
3.6.3. Port
3.6.4. Version
3.7. Feed Engine
3.7.1. Port (synchronized)
3.7.2. Wait for Full Epoch
3.7.3. Port (unsynchronized)
3.7.4. File
3.7.5. Sampling
3.8. Ephemeris Corrections
3.8.1. Directory
3.8.2. Interval
3.8.3. Port
3.8.4. Wait for Full Epoch
3.9. Monitor
3.9.1. Observation Rate
3.9.2. Failure Threshold
3.9.3. Recovery Threshold
3.9.4. Pause
3.9.5. Script
3.9.6. Performance Log
3.10. RTCM Scan
3.10.1. Mountpoint
3.11. Mountpoints
3.11.1. Add Mountpoints
3.11.2. Broadcaster Host and Port
3.11.3. Broadcaster User and Password
3.11.4. Get Table
3.11.5. Delete Mountpoints
3.11.6. Edit Mountpoints
3.11.7. Reconfigure Mountpoints On-the-fly
3.12. Start
3.13. Stop
3.14. Command Line Options
3.14.1. No Window Mode
3.14.2. Offline Mode
The 'File' button lets you
The 'Help' button provides access to
BNC comes with a help system providing online information about its functionality and usage. Short descriptions are available for any widget. Focus to the relevant widget 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; they then click the relevant widget to pop up the help text.
3.3. Proxy - for usage in a protected LAN
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.
The following defines general settings for BNC's logfile, file handling and reconfiguration on-the-fly.
Records of BNC's activities are shown in the Log section on the bottom of the main window. These logs can be saved into a file when a valid path is specified in the 'Log (full path)' field. The message log covers 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 'Log (full path)' is an empty option field, meaning that BNC logs will not saved into a file.
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.
3.4.3 Reread Configuration - optional
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. 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. See annexed section 'Configuration File' for a Unix/Linux/Mac configuration file example and a list of on-the-fly changeable options.
Observations will be converted to RINEX if they come in either RTCM Version 2.x, RTCM Version 3.x, or RTIGS format. BNC's RINEX Observation files generally contain C1, C2, P1, P2, L1, L2, S1, and S2 observations. In case an observation is unavailable, its value is set to zero '0.000'. Note that the 'RINEX TYPE' field in the RINEX Observation file header is always set to 'M(MIXED)' even if the file does not contain any GLONASS or SABAS data.
RINEX file names are derived by BNC from the first 4 characters of the corresponding 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 are 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 file name. For example, when simultaneously retrieving data from mountpoints FRANKFURT and FRANCE, their hourly RINEX 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 file name leading i.e. to hourly RINEX Observation files like
BRUS{ddd}{h}_0.{yy}O
BRUS{ddd}{h}_1.{yy}O.
Note that RINEX file names for all intervals less than 1 hour follow the file name convention for 15 minutes RINEX Observation files i.e.
FRAN{ddd}{h}{mm}.{yy}O
where 'mm' is the starting minute within the hour.
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.
3.5.3 File Interval - mandatory if 'Directory' is set
Select the length of the RINEX Observation file generated. The default value is 15 minutes.
3.5.4 Sampling - mandatory if 'Directory' is set
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.
3.5.5 Skeleton Extension - optional
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 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 the Brussels EPN station.
However, sometimes public RINEX header skeleton files are not available, its 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 'Directory' with a 'Skeleton extension' is interpreted by BNC as a personal RINEX header skeleton file for the corresponding stream.
Examples for personal skeleton file name convention: RINEX Observation files for mountpoints WETTZELL, FRANKFURT and FRANCE (same 4Char Station ID), BRUS0 from www.euref-ip.net and BRUS0 from www.igs-ip.net (same 4Char Station ID, identical mountpoint stings) would accept personal skeleton files named
WETT.skl
FRAN_KFURT.skl
FRAN_CE.skl
BRUS_0.skl
BRUS_1.skl
if RINEX 'Skeleton extension' is set to 'skl'.
Note the following regulations regarding personal RINEX header skeleton files:
If neither a public nor a personal RINEX header skeleton file is available for BNC, a default header will be used.
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 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 2 or 3 minutes after the end of each RINEX file 'Interval'.
The default format for RINEX Observation files is RINEX Version 2.11. Select 'Version 3' if you would like to save observations in RINEX Version 3 format.
Broadcast ephemeris can be saved as RINEX Navigation files when received via RTCM Version 3.x as message types 1019 (GPS) and 1020 (GLONASS) or via RTIGS records type 300. The file name convention follows the details given in section 'RINEX File Names' except that the first four characters are 'BRDC' and the last character is
Specify the 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.
3.6.2 Interval - mandatory if 'Directory' is set
Select the length of the RINEX Navigation file generated. The default value is 1 day.
BNC can output broadcast ephemeris in RINEX Version 3 ASCII format on your local host (IP 127.0.0.1) through an IP 'Port'. This function is introduced in order to support i.e. the 'BKG Ntrip Sate Space Server' (BNS) which transforms IGS clocks and orbits into corrections to broadcast ephemeris. 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_bnc_eph.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 in RINEX Version 3 format.
Note that this does not concern the broadcast ephemeris output throug IP port which is always in RINEX Version 3 format.
BNC can generate synchronized or unsynchronized observations epoch by epoch from all stations and satellites to feed a real-time GNSS engine. The output can be produced in a binary format through an IP port and/or a plain ASCII format to save the observations in a local file. It comprises the following observations where available:
StatID, SVPRN, GPSWeek, GPSWeeks, C1, C2, P1, P2, L1, L2, slip_cnt_L1, slip_cnt_L2, lock_timei_L1, lock_timei_L2, S1, S2, SNR1, SNR2
Note that slip_cnt stands for the cumulative loss of continuity indicator, lock_timei for the lock time indicator, and SNR for the signal-to-noise ratio 'S' mapped to integer numbers 1 to 9. In case an observation is not available, its value is set to zero '0.000'. Loss of continuity indicator and lock time indicator are set to nedative values if undefined.
3.7.1 Port (synchronized) - optional
BNC can produce synchronized observations in binary format on your local host (IP 127.0.0.1) through an IP 'Port'. Specify an IP port number here to activate this function. The default is an empty option field, meaning that no binary output is generated.
The binary output is a continuous stream in the following order:
begEpoch t_obsInternal t_obsInternal ... t_obsInternal endEpoch begEpoch t_obsInternal ...
The corresponding structures are defined as follow:
const char begEpoch[] = "BEGEPOCH";
const char endEpoch[] = "ENDEPOCH";
...
...
class t_obsInternal {
public:
int flags;
char StatID[20+1]; // Station ID
char satSys; // Satellite System ('G' or 'R')
int satNum; // Satellite Number (PRN for GPS NAVSTAR)
int slot; // Slot Number (for Glonass)
int GPSWeek; // Week of GPS-Time
double GPSWeeks; // Second of Week (GPS-Time)
double C1; // CA-code pseudorange (meters)
double C2; // CA-code pseudorange (meters)
double P1; // P1-code pseudorange (meters)
double P2; // P2-code pseudorange (meters)
double L1; // L1 carrier phase (cycles)
double L2; // L2 carrier phase (cycles)
int slip_cnt_L1; // L1 cumulative loss of continuity indicator (negative value = undefined)
int slip_cnt_L2; // L2 cumulative loss of continuity indicator (negative value = undefined)
int lock_timei_L1; // L1 last lock time indicator (negative value = undefined)
int lock_timei_L2; // L2 last lock time indicator (negative value = undefined)
double S1; // L1 signal-to noise ratio
double S2; // L2 signal-to noise ratio
int SNR1; // L1 signal-to noise ratio (mapped to integer)
int SNR2; // L2 signal-to noise ratio (mapped to integer)
};
The source code for BNC comes with an example program called 'test_bnc_qt.cpp' that allows you to read BNC's binary observation output from the IP port and print the observations in a plain ASCII format on standard output.
Note that any socket connection of an application to BNC's synchronized observations 'Port' is recorded in the Log section on the bottom of the main window together with a connection counter, leading to log records like 'New Connection # 1'.
3.7.2 Wait for Full Epoch - mandatory if 'Port (synchronized)' is set
When feeding a real-time GNSS engine waiting for synchronized input epoch by epoch, BNC drops whatever is received later than 'Wait for full 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 epoch' is 5 seconds.
Note that 'Wait for full epoch' does not effect the RINEX Observation file content. Observations received later than 'Wait for full epoch' seconds will still be included in the RINEX Observation files.
3.7.3 Port (unsynchronized) - optional
The example program 'test_bnc_qt.cpp' allows you to read BNC's unsynchronized binary observation output from the IP port and print the observations in a plain ASCII format on standard output.
Note that any socket connection of an application to BNC's unsynchronized observations 'Port' is recorded in the Log section on the bottom of the main window together with a connection counter, leading to log records like 'New Connection # 1'.
Specifies the full path to a 'File' where synchronized or unsynchronized 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. This option is primarily meant for testing and evaluation.
3.7.5 Sampling - mandatory if 'File' or 'Port' is set
Select the observation output sampling interval in seconds. A value of zero '0' tells BNC to send/store all received epochs. This is the default value.
RTCM is in the process of developing new Version 3 messages to transport satellite clock and orbit corrections in real-time. Based on the latest available proposal, the following premature messages currently under discussion have been implemented in BNC:
RTCM Version 3 streams carrying these messages may be used i.e. to support real-time Precise Point Positioning (PPP) applications.
Specify a directory for saving Ephemeris Corrections in files. If the specified directory does not exist, BNC will not create Ephemeris Correction files. Default value for Ephemeris Corrections 'Directory' is an empty option field, meaning that no Ephemeris Correction files will be created.
The file name convention for Ephemeris Correction files follows the convention for RINEX files except for the last character of the file name suffix which is set to "C".
3.8.2 Interval - mandatory if 'Directory' is set
Select the length of the Ephemeris Correction files. The default value is 1 day.
BNC can output epoch by epoch synchronized Ephemeris 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 Ephemeris Correction output via IP port is generated.
The source code for BNC comes with an example perl script 'test_bnc_eph.pl' that allows you to read BNC's Ephemeris Corrections from the IP port. In case of a stream carrying message types 4056 and 4057, the script produces ASCII records containing the following set of parameters:
The following is an example output from two RTCM Version 3 streams (CLCK1 and CLCK4) containing message types 4056 and 4057:
... 1490 115710.0 R17 18 -1.903 2.348 -1.343 -1.403 CLCK1 1490 115710.0 R10 18 -4.131 2.416 -0.646 -1.054 CLCK1 1490 115710.0 G27 97 5.291 1.201 -1.964 0.821 CLCK4 1490 115710.0 G26 14 -11.247 1.003 -1.168 0.074 CLCK4 ... 1490 115711.0 R17 18 -1.902 2.349 -1.342 -1.403 CLCK1 1490 115711.0 R10 18 -4.131 2.415 -0.647 -1.052 CLCK1 1490 115711.0 G27 97 5.288 1.200 -1.964 0.820 CLCK4 1490 115711.0 G26 14 -11.246 1.004 -1.168 0.074 CLCK4 ...
3.8.4 Wait for Full Epoch - mandatory if 'Port' is set
When feeding a real-time GNSS engine waiting epoch by epoch for synchronized Ephemeris Corrections, BNC drops (only concering IP port output) whatever is received later than 'Wait for full epoch' seconds. A value of 2 to 5 seconds could be an appropriate choice for that, depending on the latency of the incoming Ephemeris Corrections stream and the delay acceptable by your application. A message such as "COCK1: Correction overaged by 5 sec" shows up in BNC's logfile if 'Wait for full epoch' is exceeded.
At various times, the 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 corrupted stream(s) 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 file/section. 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 utilise 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 priory estimate of the expected observation rate of the incoming streams.
An empty option field (default) means that you don't want an explicit information from BNC about stream outages and incoming streams that can not be decoded and that the special procedure for handling of corrupted streams is by-passed (decoding attempt will never get paused).
3.9.2 Failure Threshold - optional
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 innundate 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'.
3.9.3 Recovery Threshold - optional
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 innundate 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'.
In case of a corrupted stream, the decoding process can be paused and decodings are then attempted again at decreasing rate. BNC will first attempt to decode again after a 30 second lag and if unsuccessful, make another attempt within 60 seconds after the previous attempt. If it is still unsuccessful, it will make another attempt to decode within 120 seconds after the previous attempt and so on. Each decoding attempt doubles the wait time since the previous attempt. The maximum wait time between attempts is limited to 960 seconds. Tick 'Pause' to activate this function. Note that it is only effective if an 'Observation rate' is specified.
Do not tick 'Pause' if you want to prevent BNC from making any decoding pause. Be aware that this may incur an unnecessary workload.
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 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 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 09:25:59Sample script for Unix/Linux/Mac systems:
#!/bin/bash sleep $((60*RANDOM/32767)) cat | mail -s "NABU: $1" email@address <<! Advisory Note to BNC User, Please note the following advisory received from BNC. Stream: $* Regards, BNC !
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 avoids overloading your mail server in case of a simultaneous failure of many streams.
3.9.6 Performance Log - optional
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
BNC can average the latencies per stream over a certain period of GPS time, the 'Performance log' interval. Mean latencies are calculated from the individual latencies of at most one (first incoming) observation or correction to Broadcast Ephemeris per second. Note that computing correct latencies requires the clock of the host computer to be properly synchronized.
Statistics: BNC counts the number of GPS seconds covered by at least one observation. It also estimates an observation rate (independent from the a priory specified 'Observation rate') from all observations received throughout the first full 'Performance log' 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 file/section at the end of each 'Performance log' interval. A typical output from a 1 hour 'Performance log' 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 'Performance log' 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 setup interface may not provide details about RTCM message types. As reliable information concerning stream contents should be available i.e. for NTRIP broadcaster operators to maintain the broadcaster's sourcetable, BNC allows to scan RTCM streams for incoming message types and printout some of the contained meta-data. The idea for this option arose from 'InspectRTCM', a comprehensive stream analyzing tool written by D. Stoecker.
Specify the mountpoint of an RTCM Version 3.x stream to scan it and log all contained
Specify the mountpoint of an RTCM Version 2.x stream to scan it and log all contained
Note that in RTCM Version 2.x the message types 18 and 19 carry only the observables of one frequence. Hence it needs two type 18 and 19 messages per epoch to transport the observations from dual frequency receivers.
Logged time stamps refer to message reception time and allow to understand 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.
Each stream on an NTRIP broadcaster is defined using a unique source ID called mountpoint. An NTRIP client like BNC access the desired data stream by referring to its mountpoint. Information about mountpoints is available through the source-table maintained by the NTRIP broadcaster. Note that mountpoints could show up in BNC more than once when retrieving streams from several NTRIP broadcasters.
Streams selected for retrieval are listed under the 'Mountpoints' section on BNC's main window. The list provides the following information extracted from source-table(s) produced by the NTRIP broadcasters:| 'broadcaster:port' | NTRIP broadcaster URL and port. |
| 'mountpoint' | Mountpoint on NTRIP broadcaster. |
| 'decoder' | Type of decoder used to handle the incoming stream content according to its format; editable. |
| 'lat' | Approximate latitude of reference station, in degrees, north; editable if 'nmea' = 'yes'. |
| 'long' | Approximate longitude of reference station, in degrees, east; editable if 'nmea' = 'yes'. |
| 'nmea' | Indicates whether or not streaming needs to be initiated by BNC through sending NMEA-GGA message carrying position coordinates in 'lat' and 'long'. |
| 'bytes' | Number of bytes retrieved. |
Button 'Add Mountpoints' opens a window that allows user to select data streams from an NTRIP broadcaster according to their mountpoints.
3.11.2 Broadcaster Host and Port - required
Enter the NTRIP broadcaster host IP and port number. http://www.rtcm-ntrip.org/home provides information about known NTRIP broadcaster installations. Note that EUREF and IGS operate NTRIP broadcasters at http://www.euref-ip.net/home and http://www.igs-ip.net/home.
3.11.3 Broadcaster User and Password - required for protected streams
Some streams on NTRIP broadcasters may be restricted. Enter a valid 'User' ID and 'Password' for access to protected streams. Accounts are usually provided per NTRIP broadcaster through a registration procedure. Register through http://igs.bkg.bund.de/index_ntrip_reg.htm for access to protected streams on www.euref-ip.net and www.igs-ip.net.
Use the 'Get Table' button to download the source-table from the NTRIP broadcaster. Pay attention to data fields 'format' and 'format-details'. Keep in mind that BNC can only decode and convert streams that come in RTCM Version 2.x, RTCM Version 3.x, or RTIGS format. RTCM Version 2.x streams must contain message types 18 and 19 or 20 and 21 while RTCM Version 3.x streams must contain GPS or SBAS message types 1002 or 1004 and may contain GLONASS message types 1010 or 1012, see data field 'format-details' for available message types and their repetition rates in brackets. Note that in order to produce RINEX Navigation files RTCM Version 3.x streams containing message types 1019 (GPS) and 1020 (GLONASS) are required. Select your streams line by line, use +Shift and +Ctrl when necessary.
The contents of data field 'nmea' tells you whether a stream retrieval needs to be initiated by BNC through sending an NMEA-GGA message carrying position coordinates (virtual reference station).
Hit 'OK' to return to the main window. If you wish you can click on 'Add Mountpoints' and repeat the process again to retrieve mountpoints from different casters.
To remove a stream from the 'Mountpoints' list in the main window, highlight it by clicking on it and hit the 'Delete Mountpoints' button. You can also remove multiple mountpoints simultaneously by highlighting them using +Shift and +Ctrl.
3.11.7 Reconfigure Mountpoints On-the-fly
The mountpoints selection can be changed on-the-fly without interrupting uninvolved threads in the running BNC process.
Window mode: Hit 'Save & Activate Options' while BNC is in window mode and already processing data to let changes of your mountpoints selection immediately become effective.
No window mode: When operating BNC online in 'no window' mode (command line option -nw), you force BNC to reread its 'mountPoints' configuration option in pre-defined intervals. Select '1 min', '1 hour', or '1 day' as 'Reread configuration' option to reread the 'mountpoints' option every full minute, hour, or day. This lets a 'mountPoints' option edited in between in the configuration file or Windows register become effective without terminating uninvolved threads. See annexed section 'Configuration File' for a Unix/Linux/Mac configuration file example and a list of other on-the-fly changeable options.
Hit 'Start' to start retrieving, decoding, and 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 data from a file in offline mode. BNC will then use processing options from the configuration file (Unix/Linux/Mac) or from the register BKG_NTRIP_Client (Windows). Note that the self-explaining contents of the configuration file or the Windows register can easily be edited.
3.14.1 No Window Mode - optional
Apart from its regular windows mode, BNC can be started on all systems as a background/batch job with command line option '-nw'. BNC will then run in 'no window' mode, using processing options from its configuration file. Terminate BNC using Windows Task Manager when running it in 'no window' mode on Windows systems.
Example:
bnc.exe -nw
3.14.2 Offline Mode - optional
Although BNC is primarily a real-time online tool, it can be run in offline mode to read data from a file for post processing purposes. Enter the following four command line options for that:
Example:
./bnc --file FFMJ.dat --format RTCM_3 --date 2008-10-27 --time 23:12:56
Note that it is necessary to define a date and time for the first epoch because RTCM streams do not contain complete time stamps as needed for RINEX. Note further that when running BNC in offline mode, it will use options for file saving, interval, sampling etc. from its configuration file.
The BKG Ntrip Client (BNC) Qt Graphic User Interface (GUI) has been developed for the Federal Agency for Cartography and Geodesy (BKG) by Leos Mervart, Czech Technical University Prague, Department of Geodesy. BNC includes the following GNU GPL software components:
Georg Weber
Federal Agency for Cartography and Geodesy (BKG)
Frankfurt, Germany
[euref-ip@bkg.bund.de] or [igs-ip@bkg.bund.de]
Acknowledgements
BNC's Help Contents has been proofread by Thomas Yan, University of New South Wales, Australia.
Scott Glazier, OmniSTAR Australia, included the decoding of broadcast ephemeris from RTIGS streams and has been helpful in finding BNC's bugs.
James Perlt, BKG, helped fixing bugs and redesigned BNC's main window.
Andre Hauschild, German Space Operations Center, DLR, revised the RTCMv2 decoder.
Zdenek Lukes, Czech Technical University Prague, Department of Geodesy, extended the RTCMv2 decoder to handle message types 3, 20, 21, and 22 and added loss of lock indicator.
8.1. History
8.2. RTCM
8.2.1 NTRIP
8.2.2 RTCM Version 2.x
8.2.3 RTCM Version 3.x
8.3. RTIGS
8.3.1 SOC
8.4. Configuration File
8.5. Links
| Dec 2006 | Version 1.0b | [Add] First Beta Binaries published based on Qt 4.2.3. |
| Jan 2007 | Version 1.1b | [Add] Observables C2, S1, and S2 [Add] Virtual reference station access [Bug] RTCM2 decoder time tag fixed [Mod] Small letters for public RINEX skeleton files [Add] Online help through Shift+F1 |
| Apr 2007 | Version 1.2b | [Bug] Output only through IP port [Bug] Method 'reconnecting' now thread-save [Add] ZERO decoder added [Mod] Download public RINEX skeletons once per day [Mod] Upgrade to Qt Version 4.2.3 [Mod] Replace 'system' call for RINEX script by 'QProcess' [Add] HTTP Host directive for skeleton file download [Add] Percent encoding for user IDs and passwords [Bug] Exit execution of calling thread for RTCM3 streams [Bug] Signal-slot mechanism for threads |
| May 2007 | Version 1.3 | [Add] Source code published. |
| Jul 2007 | Version 1.4 | [Bug] Skip messages from proxy server [Bug] Call RINEX script through 'nohup' |
| Apr 2008 | Version 1.5 | [Add] Handle ephemeris from RTCM Version 3.x streams [Add] Upgrade to Qt Version 4.3.2 [Add] Optional RINEX v3 output [Add] SBAS support [Bug] RINEX skeleton download following stream outage [Add] Handle ephemeris from RTIGS streams [Add] Monitor stream failure/recovery and latency [Mod] Redesign of main window [Bug] Freezing of About window on Mac systems [Bug] Fixed problem with PRN 32 in RTCMv2 decoder [Bug] Fix for Trimble 4000SSI receivers in RTCMv2 decoder [Mod] Major revision of input buffer in RTCMv2 decoder |
| Dec 2008 | Version 1.6 | [Mod] Fill blanc columns in RINEXv3 with 0.000 [Add] RTCMv3 decoder for clock and orbit corrections [Add] Check RTCMv3 streams for incoming message types [Add] Decode RTCMv2 message types 3, 20, 21, and 22 [Add] Loss of lock and lock time indicator [Bug] Rounding error in RTCMv3 decoder concerning GLONASS height [Mod] Accept GLONASS in RTCMv3 when transmitted first [Add] Leap second 1 January 2009 [Add] Offline mode, read data from file [Add] Output antenna descriptor, coordinates and excentricities from RTCMv3 [Add] Reconfiguration on-the-fly [Mod] Binary ouput of synchronized observations [Add] Binary output of unsynchronized observations [Bug] Fixed problem with joined RTCMv3 blocks |
| Jan 2009 | Version 1.7 |
[Add] Support Pentagon proxies [Mod] Ntrip sourcetable request |
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 1.0 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:
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: 'identifiey', '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'.
Transmitting GNSS carrier phase data can be done through RTCM Version 2.x messages. Please note that only RTCM Version 2.2 and 2.3 streams may include GLONASS data. Messages that may be of some interest here are:
RTCM Version 3.x has been developed as a more efficient alternative to RTCM Version 2.x. 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.x standard is intended to correct these weaknesses.
RTCM Version 3.x defines a number of message types. Messages that may be of interest here are:
RTIGS stands for a data format and transport protocol for GPS observations. It was defined by the Real-Time IGS Working Group (RTIGS WG). Its definition is based on the SOC format. Every RTIGS record has one of the following numbers:
Station record number 100
Observation record (O_T) number 200
Ephemeris record (E_T) number 300
Meteorological record (M_T) number 400
Every station has one of the following unique numbers:
1-99 reserved for JPL
100-199 reserved for NRCan
200-299 reserved for NGS
300-399 reserved for ESOC
400-499 reserved for GFZ
500-599 reserved for BKG
600-699 reserved for GEOSCIENCE AUS
700-799 others
etc
The number of bytes in each real time message includes the header as well as the data content, but NOT the pointer.
For example:
All records are related to a station configuration indicated by the Issue of Data Station (IODS). The IODS will enable the user to identify the equipment and software that was used to derive the observation data.
Each record header contains the GPS Time in seconds which flows continuously from 6 Jan-1980 onwards.
The data payload of each record consists of observations. The structures indicate a pointer to data but in fact the broadcast messages do not contain the pointer, only the data. Users will have to manage the data and the pointer is shown in order to illustrate where the data is located in the message and one possible data management option.
All record data are in network byte order (Big Endian), i.e. IA32 users have to swap bytes.
Visit http://igscb.jpl.nasa.gov/mail/igs-rtwg/2004/msg00001.html for further details.
The SOC format has been designed in July 1999 by the Jet Propulsion Laboratory (JPL) and the California Institute of Technology (CalTech) to transport 1Hz GPS data with minimal bandwidth over the open Internet. SOC follows the 'little-endian' byte order meaning that the low-order byte of a number is stored in memory at the lowest address, and the high-order byte at the highest address. Because the transport layer is UDP, the format does not include sync bits, a checksum, or cyclic redundancy checksum (CRC). SOC allows to transport the GPS observable CA, P1, P2, L1, and L2, efficiently compressed down to 14 bytes with 1 mm range resolution and 0.02 mm phase resolution. SOC contains epochs for cycle slips, a stand-alone time-tag per epoch, a minimum representation of the receiver's clock solution, 3 SNR numbers, a unique site id, a modulo 12 hour sequence number and flags for receiver type and GPS health. SOC's simple structure comprises an 8 byte header, a 9 byte overhead for timetag, number of gps, etc., plus 21 data bytes per gps.
Visit http://gipsy.jpl.nasa.gov/igdg/papers/SOC_FORMAT.ppt for further details.
The following is an example for the contents of a Unix/Linux/Mac configuration file ${HOME}/.config/BKG/BKG_NTRIP_Client.conf. It enables the retrieval of stream ACOR0 form www.euref-ip.net and FFMJ3 from www.igs-ip.net for the generation of 15 min RINEX files. RINEX files are uploaded to an archive using script 'up2archive' :
[General] adviseFail=15 adviseReco=5 adviseScript= binSampl=0 casterHost=www.euref-ip.net casterHostList= casterPassword=pass casterPort=80 casterUser=user corrIntr=1 day corrPath= corrPort= corrTime=5 ephIntr=1 day ephPath=/home/user/rinex ephV3=2 logFile=/home/user/log.txt makePause=0 mountPoints=//user:pass@www.euref-ip.net:2101/ACOR0 RTCM_2.3 43.36 351.60 no, //user:pass@www.igs-ip.net:2101/FFMJ3 RTCM_3.0 41.58 1.40 no obsRate= onTheFlyInterval=1 day outEphPort=2102 outFile=/home/user/ascii outPort=2101 outUPort= perfIntr= proxyHost=proxyhost proxyPort=8001 rnxAppend=2 rnxIntr=15 min rnxPath=/home/user/rinex rnxSampl=0 rnxScript=/home/user/up2archive rnxSkel=SKL rnxV3=2 waitTime=5
Note that on Windows systems configuration options are saved in register BKG_NTRIP_Client.
Note further that configuration options that can be changed/edited on-the-fly while BNC is already processing data are
| NTRIP | http://igs.bkg.bund.de/index_ntrip.htm |
| EUREF-IP NTRIP broadcaster | http://www.euref-ip.net/home |
| IGS-IP NTRIP broadcaster | http://www.igs-ip.net/home |
| NTRIP broadcaster overview | http://www.rtcm-ntrip.org/home |
| EUREF-IP Project | http://www.epncb.oma.be/euref_IP |
| Real-time IGS Pilot Project | http://www.rtigs.net/pilot |
| Radio Technical Commission for Maritime Services | http://www.rtcm.org |