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 the EUREF-IP Pilot Project (EUREF-IP, IP for Internet Protocol) and the Real-Time IGS Working Group (RTIGS WG).
BNC is written under GNU General Public License (GPL). Binaries for BNC are available for Windows, Linux, and Solaris systems. It is likely that BNC can be compiled on other systems where a GNU compiler and Qt Version 4.0.1 are installed.
The purpose of BNC is to
BNC decodes and converts GNSS data streams carrying code and phase data coming in
Warning
BNC has the capacity to retrieve hundreds of GNSS data streams simultaneously. Please understand that it is a powerful tool that may generate a heavy workload on the NTRIP broadcaster side depending on the number of streams it requests. It is recommended to limited the number of streams where possible to avoid unnecessary workload.
B - 1. File
B - 2. Help
B - 3. Proxy
B - 4. Synchronized Output
B - 4.1. Wait for Full Epoch
B - 4.2. ASCII Output File
B - 4.3. Port for Binary Output
B - 5. RINEX
B - 5.1. RINEX Directory
B - 5.2. RINEX Script
B - 5.3. RINEX File Interval
B - 5.4. RINEX Sampling
B - 5.5. RINEX Skeleton Extension
B - 5.6. Append Files
B - 6. Mountpoints
B - 6.1. Add Mountpoints
B - 6.2. Broadcaster Host and Port
B - 6.3. Broadcaster User and Password
B - 6.4. Get Table
B - 6.5. Delete Mountpoints
B - 6.6. Edit Mountpoints
B - 7. Log
B - 8. Start
B - 9. Stop
B - 10. No Window
The 'File' button lets you
The 'Help' button provides access to
You may like to run BNC in a Local Area Network (LAN). LAN's are often protected by a proxy server. 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 out the proxy server settings of your Internet browser or ask your network administrator.
Note that IP streaming may be generally denied in a LAN. In such a case you need to request an appropriate modification of the security policy from your network administrator or ask for the installation of a TCP relay to involved NTRIP broadcasters. If that doesn't work out, run BNC outside your LAN on a host that is connected to the Internet through an Internet Service Provider (ISP).
BNC lets you output synchronized observations epoch by epoch. This output is made available in a plain ASCII format and in a binary format. The output comprises the following observations if available:
StatID, SVPRN, GPSWeek, GPSWeeks, C1, P1, P2, L1, L2, SNR1, SNR2.In case an observation is unavailable, its value is set to zero '0.000'.
When feeding a real-time GNSS engine waiting for input epoch by epoch, BNC ignores whatever is received later then 'Wait for full epoch' seconds. A value of 3 to 5 seconds may be an appropriate choice for that, depending on the latency of the incoming streams and the delay you can accept for your real-time GNSS product. Default value for 'Wait for full epoch' is 1 second.
Note that 'Wait for full epoch' does not influence the RINEX file contents. Observations received later than 'Wait for full epoch' seconds will still be included in the RINEX files.
Enter the full path for a file to save synchronized observations in a plain ASCII format. Default value is an empty option field, meaning that no ASCII output file is created.
BNC makes synchronized observations available in a binary format on your local host (IP 127.0.0.1) through an IP port. Enter an IP port number to activate this function. Default is an empty option field, meaning that no binary output is generated.
The binary output is provided as a continuous stream in the order
begEpoch begObs Observation begObs Observation begObs Observation ... endEpoch begEpoch ...
where the corresponding structures are defined as
const char begEpoch = 'A';
const char begObs = 'B';
const char endEpoch = 'C';
struct Observation {
char StatID[5+1]; // Station ID
int SVPRN; // Satellite PRN
int GPSWeek; // Week of GPS-Time
double GPSWeeks; // Second of Week (GPS-Time)
double C1; // 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 SNR1; // L1 signal-to noise ratio (0.1 dB)
int SNR2; // L2 signal-to noise ratio (0.1 dB)
} ;
Observations are converted to RINEX Version 2.1. RINEX file names are derived by BNC from the first 4 characters of the corresponding mountpoint (4Char Station ID) while omitting the residual part of the mountpoint string. Thus, retrieving data from mountpoints FRANKFURT and WETTZELL leads to 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.
For those streams that show mountpoints with an identical 4Char Station ID (same first 4 characters), the mountpoint strings are split in two sub-strings and both become part of the RINEX file name. Example: When simultaneously retrieving data from mountpoints FRANKFURT and FRANCE, their hourly RINEX observation file names are defined as
FRAN{ddd}{h}_KFURT.{yy}
FRAN{ddd}{h}_CE.{yy}O
If several streams show exactly the same mountpoint (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.
BNC's RINEX observation files generally contain C1, P1, P2, L1, and L2 observations. In case an observation is unavailable, its value is set to zero '0.000'. Note that even if a RINEX file does not contain GLONASS data, the 'RINEX TYPE' field in the RINEX file header is set to 'M (MIXED)'.
Enter a path for saving the RINEX files in a directory. If this directory does not exist, BNC will not create RINEX files. Default value for 'RINEX directory' is an empty option field, meaning that streams are not converted to RINEX.
Whenever a RINEX file is saved, you may like to compress, copy, or upload it immediately via FTP. For that you enter the full path of a script or batch file carrying out these operations. The RINEX file path will be passed to the script as a command line parameter (%1 on Windows systems, $1 on Unix/Linux systems).
Select the interval for the RINEX file generation. Default for 'RINEX file interval' is 15 minutes.
Select the RINEX sample interval in seconds. Zero '0' stands for converting all incoming epochs to RINEX. Default for RINEX 'Sampling' is '0'.
BNC lets you introduce RINEX header skeleton files that contain the header records you would like to see instead of a default header. You may like to derive RINEX skeleton files from the information given in sitelogs. A file in the 'RINEX directory' with the 'RINEX skeleton extension' is understood by BNC as a RINEX header skeleton file for the affected stream.
Example: RINEX 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 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 conditions regarding RINEX header skeleton files:
When starting BNC, new RINEX files are created by default. Probably existing files are overwritten. However, it may be desirable to append observations to already existing RINEX files following a restart of BNC after an intentional 'Stop', a system crash, or a crash of BNC. Hit 'Append files' to continue with already existing files and thus save what has been recorded so far. Note that the option 'Append files' also concerns the 'ASCII output file' and the 'Log' file.
Each stream on an NTRIP broadcaster is defined through a unique source ID called mountpoint. An NTRIP client like BNC can access the data of a desired stream by its mountpoint. Information about mountpoints is available through the sourcetable maintained by the NTRIP broadcaster. Note that it may happen that mountpoints show up in BNC more than once when retrieving streams from several NTRIP broadcasters.
Button 'Add Mountpoints' opens a window that lets you select data streams from an NTRIP broadcaster by their mountpoints.
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.
Streams on NTRIP broadcasters may be password protected. Enter a valid 'User' ID and 'Password' for access to protected NTRIP broadcaster 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.
Hit button 'Get Table' to download the sourcetable from the NTRIP broadcaster. Pay attention to data fields 'format' and 'format-details'. Have in mind that BNC can only decode and convert streams that come in RTCM 2.x, RTCM 3, or RTIGS format. RTCM 2.x streams must contain message types 18 and 19 while RTCM 3 streams must contain message types 1001 or 1003, better 1003 or 1004 (GPS), 1009 or 1010, better 1011 or 1012 (GLONASS), see data field 'format-details' for available message types and their repetition rates in brackets. Select your streams line by line, use +Shift and +Ctrl when necessary.
Hit 'OK' to return to the main window. You may like to 'Add Mountpoints' from another NTRIP broadcaster when necessary.
To delete a stream shown under 'Mountpoints' in the main window select it by mouse click and hit 'Delete Mountpoints'. For simultaneous deletion of several streams highlight them using +Shift and +Ctrl.
BNC automatically selects one out of several incorporated decoders for a stream based on its 'format' and 'format-details' as given in the sourcetable. It may happen that you need to overrule the automated decoder selection because of sourcetable setup deficiencies. Therefore BNC allows to edit (double-click) the decoder string for each stream shown under 'Mountpoints'. Accepted decoder strings allowed to be introduced are 'RTCM_2.x', 'RTCM_3', and 'RTIGS'.
BNC comments its activities in the 'Log' section on the main windows. Comments can be saved and concatenated in a file when entering a full path for 'Log' file. Information is given about the communication between BNC and the NTRIP broadcaster as well as about problems that may occur concerning communication link, stream availability, stream delay, stream conversion etc. Default value for 'Log' is an empty option field, meaning that BNC comments are not saved in 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 files and thus overwrite probably existing files when necessary unless option 'Append files' is set.
Hit the 'Stop' button to stop BNC.
You can use BNC on all systems in batch mode with the command line option -nw. BNC then runs in 'no window' mode, reading options from the configuration file ${HOME}/.config/BKG/BNC_NTRIP_Client.conf (Unix/Linux) or from the register BKC_NTRIP_Client (Windows).
Note that the self-explaining contents of the configuration file or the Windows register can easily be edited. Terminate BNC using the 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 Advanced Geodesy. BNC integrates the following GNU GPL software components:
Note that this is a beta version of BNC provided for test and evaluation. Make sure you installed the latest version available from http://igs.bkg.bund.de/index_ntrip_down.htm. We are still working on the program and would appreciate if you could send your comments, suggestions, or bug reports to:
Georg Weber
Federal Agency for Cartography and Geodesy (BKG)
Frankfurt, Germany
euref-ip@bkg.bund.de
| 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 Pilot Project | http://www.epncb.oma.be/euref_IP |
| Real-Time IGS Working Group | http://igscb.jpl.nasa.gov/projects/rtwg/index.html |
F - 1. NTRIP
E - 1.1 Sourcetable
F - 2. RTCM
F - 2.1 RTCM Version 2.x
F - 2.2 RTCM Version 3
F - 3. RTIGS
F - 3.1 SOC
'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 sourcetable containing information on available NTRIP streams, networks of NTRIP streams, and NTRIP broadcasters. The sourcetable is sent to an NTRIP client on request. Sourcetable records are dedicated to one of the following: Data Streams (record type STR), Casters (record type CAS), or Networks of streams (record type NET).
Sourcetable 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'.
Sourcetable records of type NET contain the following data fields: 'identifiey', 'operator', 'authentication', 'fee', 'web-net', 'web-str', 'web-reg', 'misc'.
Sourcetable 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 government and non-government 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) and handled by the Special Committee SC 104.
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. Note that only RTCM Version 2.3 streams may include GLONASS data. Messages that may be of interest here are of type 1, 2, 3, 6, 9, 16,18/19, 20/21, and 22.
RTCM Version 3 has been developed as a more efficient alternative to RTCM 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 standard is intended to correct these weaknesses.
RTCM Version 3 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 (no GLONASS). It has been 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 is continuous from 6 Jan-1980.
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 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 (no GLONASS) 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.