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. It is likely that BNC can be compiled on other systems where a GNU compiler and Qt Version 4.3.2 are installed.
The purpose of BNC is to
BNC supports the following GNSS data formats:
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.
Note that running BNC requires the clock of the host computer to be properly synchronized.
BNC 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.
3.1. File
3.2. Help
3.3. Proxy
3.4. Synchronized Output
3.4.1. Wait for Full Epoch
3.4.2. ASCII Output File
3.4.3. Port for Binary Observation Output
3.4.4. Port for ASCII Ephemeris Output
3.5. RINEX
3.5.1. RINEX File Names
3.5.2. RINEX Directory
3.5.3. RINEX Version
3.5.4. RINEX Script
3.5.5. RINEX File Interval
3.5.6. RINEX Sampling
3.5.7. RINEX Skeleton Extension
3.5.8. Append Files
3.6. Ephemeris
3.6.1. Ephemeris Directory
3.6.2. RINEX Version
3.6.3. Ephemeris File Interval
3.7. Advisory Note
3.7.1. Inspect Segment
3.7.2. Failure Threshold
3.7.3. Recovery Threshold
3.7.4. Advisory Script
3.8. Mountpoints
3.8.1. Add Mountpoints
3.8.2. Broadcaster Host and Port
3.8.3. Broadcaster User and Password
3.8.4. Get Table
3.8.5. Delete Mountpoints
3.8.6. Edit Mountpoints
3.9. Log
3.10. Start
3.11. Stop
3.12. No Window
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.
BNC can generate synchronized epoch by epoch observations from all stations and satellites. The output can be in either a plain ASCII format and/or a binary format. It comprises the following observations where available:
StatID, SVPRN, GPSWeek, GPSWeeks, C1, C2, P1, P2, L1, L2, S1, S2, SNR1, SNR2
Note that SNR stands 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'.
3.4.1 Wait for Full Epoch - optional
When feeding a real-time GNSS engine waiting for 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.
3.4.2 ASCII Output File - optional
Specifies 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. This option is primarily meant for testing and evaluation.
3.4.3 Port for Binary Observation Output - 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 begObs Observation begObs Observation begObs Observation ... endEpoch begEpoch ...
with the corresponding structures defined as follow:
const char begEpoch = 'A';
const char begObs = 'B';
const char endEpoch = 'C';
struct Observation {
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)
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.
3.4.4 Port for ASCII Ephemeris Output - optional
BNC can output broadcast ephemeris in binary 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 called 'test_bnc_eph.pl' that allows you to read BNC's ASCII ephemeris output from the IP port.
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.
3.5.2 RINEX Directory - optional
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 'RINEX directory' is an empty option field, meaning that no RINEX Observation files will be written.
3.5.3 RINEX Version - optional
The default format for RINEX Observation files is RINEX Version 2.11. Select 'RINEX v3' if you would like to save observations in RINEX Version 3 format.
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 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'.
3.5.5 RINEX File Interval - mandatory if 'RINEX directory' is set
Select the length of the RINEX Observation file generated. The default value is 15 minutes.
3.5.6 RINEX Sampling - mandatory if 'RINEX 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.
3.5.7 RINEX 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 the extension 'RINEX 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.
When BNC is started, new RINEX Observation files are created by default and any existing files with the same name will be overwritten. However, users might want to append observations and ephemeris to existing RINEX 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' also affects RINEX Navigation files, the 'ASCII output file' and the 'Log' file.
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 'BNC_' and the last character is
3.6.1 Ephemeris Directory - optional
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 RINEX Version - optional
Default format for RINEX Navigation files containing broadcast ephemeris is RINEX Version 2.11. Select 'RINEX v3' if you want to save the ephemeris in RINEX Version 3 format.
3.6.3 Ephemeris Interval - mandatory if 'Ephemeris directory' is set
Select the length of the RINEX Navigation file generated. The default value is 1 day.
At various times, the incoming stream might become unavailable or corrupted. In such cases, it is important that the BNCoperator 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.
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 in2 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 'Inspect Segment' time span and then determines whether the content of that segment is valid or corrupted. If it is corrupted, the decoding process is 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.
3.7.1 Inspect Segment - mandatory for 'Failure' and 'Recovery' thresholds
BNC buffers all the results (both valid and invalid) returned by the decoder within a short 'Inspect Segment' time and then determines whether the stream is corrupted or not. If all the results observed within the 'Inspect Segment' time span are invalid this segment is then reported as bad segment. The default value of 15 seconds for 'Inspect Segment' is recommended when handling 1Hz data. If the specified value is too small and temporary communication bottlenecks occur, this may lead to an additional data loss of some data of the affected stream.
Specifying a value of zero '0' will bypass BNC's data corruption check. Beware that this may result in unnecessary additional workload in case of prolonged stream corruption. Also note that 'Inspect Segment' must be set to greater than zero '0' in order to trigger event report on corrupted streams.
3.7.2 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 bad segments (indicating corrupted data) returned by the decoder are detected 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.
3.7.3 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 a valid observation is again received at least once within 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 both the 'Failure' and 'Recovery' thresholds will force BNC to report any stream failure or recovery immediately and decoding attempt will never get paused.
Also note that using this function for corrupted streams requires the 'Inspect Segment' value to be set to greater than zero '0'.
All the events are reported in the 'Log' file/section as a 'Begin_Outage', End_Outage', 'Begin_Corrupted' or 'End_Corrupted' message. They can also be passed on as parameters to a shell script or batch file to generate an advisory notice 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.
3.7.4 Advisory Script - optional
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 notice to network operator or stream providers. To enable this feature, specify the full path to the script or batch file in the 'Notice 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/Linuxsystems).
Leave this field empty if you do not wish to use this option. An invalid path will also disable this option.
Sample script for Unix/Linux systems:
#!/bin/bash sleep $((60*RANDOM/32767)) cat | mail -s "BNC: $2 Stream $1" email@address <<! Advisory Note to BNC User, Please note a $2 advisory from BNC for stream $1 dated `date`. 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 outage of many 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:| 'mountpoint' | NTRIP broadcaster URL, port, and mountpoint. |
| '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.
3.8.2 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.
3.8.3 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 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.
Records of BNC's activities are shown in the 'Log' section of the main windows. 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. The default value for 'Log (full path)' is an empty option field, meaning that BNC logs will not saved into a file.
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.
On all systems BNC can be started in batch mode with the command line option '-nw'. BNC will then run in 'no window' mode, using options from the configuration file ${HOME}/.config/BKG/BNC_NTRIP_Client.conf (Unix/Linux, see Config File example in the Annex) 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. Terminate BNC using Windows Task Manager when running it in 'no window' mode on Windows systems.
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:
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:
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.
8.1. History
8.2. NTRIP
8.2.1 Source-table
8.3. RTCM
8.3.1 RTCM Version 2.x
8.3.2 RTCM Version 3.x
8.4. RTIGS
8.4.1 SOC
8.5. Config File
8.6. 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' |
| Feb 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] Advisory notes following stream failure/recovery |
'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'.
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.
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 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= casterHost=www.euref-ip.net casterPassword=pass casterPort=80 casterUser=user ephIntr=1 day ephPath=/home/user/rinex ephV3=2 inspSegm=15 logFile=/home/user/log.txt 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 outEphPort=2102 outFile=/home/user/ascii outPort=2101 proxyHost=proxyhost proxyPort=8001 rnxAppend=2 rnxIntr=15 min rnxPath=/home/weber/rinex rnxSampl=0 rnxScript=/home/weber/up2archive rnxSkel=SKL rnxV3=2 waitTime=5
| 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 |