Changeset 7605 in ntrip


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Timestamp:
Dec 6, 2015, 11:08:49 PM (7 years ago)
Author:
weber
Message:

Documentation completed

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1 edited

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  • trunk/BNC/src/bnchelp.html

    r7604 r7605  
    896896
    897897<p><h4>1.7 <a name="introLBack">Looking Back</h4></p>
    898 
    899898<p>
    900899A basic function of BNC is streaming GNSS data over the open Internet using the Ntrip transport protocol. Employing IP streaming for satellite positioning goes back to the beginning of our century. Wolfgang Rupprecht has been the first who developed TCP/IP server software under the acronym of DGPS-IP (Rupprecht 2000) and published it under GNU General Public License (GPL). While connecting marine beacon receivers to PCs with permanent access to the Internet he transmitted DGPS corrections in RTCM format to support Differential GPS positioning over North America. With approximately 200 bits/sec the bandwidth requirement for disseminating beacon data was comparatively small. Each stream was transmitted over a unique combination of IP address and port. Websites informed about existing streams and corresponding receiver positions.
    901900</p>
    902 
    903 <p>
    904 To cope with an increasing number of transmitting GNSS reference stations, the Federal Agency for Cartography and Geodesy (BKG) together with the Informatik Centrum Dortmund (ICD) in Germany developed a streaming protocol for satellite navigation data called 'Networked Transport of RTCM via Internet Protocol' (Ntrip). The protocol was built on top of the HTTP standard and included the provision of meta data describing the stream contents. Any stream could now be globally transmitted over just one IP port: HTTP port 80. Stream availability and content details became part of the transport protocol. The concept was first published in 2003 (Weber et al. 2003) and based on three software components, namely an NtripServer pushing data from a reference station to an NtripCaster and an NtripClient pulling data from the splitter caster to support a rover receiver. (Note that from a socket-programmers perspective NtripServer and NtripClient both act as clients; only the NtripCaster operates as socket-server.) Ntrip could essentially benefit from Internet Radio developments. It was the ICECAST mulitmedia server which provided the bases for BKG's 'Professional Ntrip Broadcaster' with software published first in 2003 and of course again as Open Source under GPL.
    905 </p>
    906 
     901<p>
     902To cope with an increasing number of transmitting GNSS reference stations, the Federal Agency for Cartography and Geodesy (BKG) together with the Informatik Centrum Dortmund (ICD) in Germany developed a streaming protocol for satellite navigation data called 'Networked Transport of RTCM via Internet Protocol' (Ntrip). The protocol was built on top of the HTTP standard and included the provision of meta data describing the stream contents. Any stream could now be globally transmitted over just one IP port: HTTP port 80. Stream availability and content details became part of the transport protocol. The concept was first published in 2003 (Weber et al. 2003) and based on three software components, namely an NtripServer pushing data from a reference station to an NtripCaster and an NtripClient pulling data from the stream splitting caster to support a rover receiver. (Note that from a socket-programmers perspective NtripServer and NtripClient both act as clients; only the NtripCaster operates as socket-server.) Ntrip could essentially benefit from Internet Radio developments. It was the ICECAST mulitmedia server which provided the bases for BKG's 'Professional Ntrip Broadcaster' with software published first in 2003 and of course again as Open Source under GPL.
     903</p>
    907904<p>
    908905For BKG as a governmental agency, making Ntrip an Open Industry Standard has been an objective from the very beginning. The 'Radio Technical Commission for Maritime Services' (RTCM) accepted 'Ntrip Version 1' in 2004 as 'RTCM Recommended Standard' (Weber et al. 2005). Nowadays there is almost no geodetic GNSS receiver which does not come with integrated NtripClient and NtripServer functionality as part of the firmware. Hundreds of NtripCaster implementations are operated world-wide for highly accurate satellite navigation through RTK networks. Thousands of reference stations upload observations via NtripServer to central computing facilities for any kind of NtripClient application. In 2011 'Ntrip Version 2' was released (RTCM SC-104 2011) which cleared and fixed some design problems and HTTP protocol violations. It also supports TCP/IP via SSL and adds optional communication over RTSP/RTP and UDP.
    909906</p>
    910 
    911 <p>
    912 With the advent of Ntrip as open streaming standard, BKG's interest turned towards taking advantage from free real-time access to GNSS observations. NGOs such as the IAG Reference Frame Sub Commissions for Africa (AFREF), Asia & Pacific (APREF), Europe (EUREF), North America (NAREF) Latin America & Caribbean (SIRGAS), and the International GNSS Service (IGS) maintain continental or even global GNSS networks with the majority of modern receivers supporting Ntrip stream upload. Through operating BKG's NtripCaster software, these networks became extremely valuable sources of real-time GNSS information.  In 2005 this was the starting point for developing the 'BKG Ntrip Client' (BNC) as a multi-stream Open Source NtripClient which allows pulling hundreds of streams simultaneously from any number of NtripCaster installations world-wide. Decoding incoming RTCM streams and output observations epoch by epoch through IP port to feed a real-time GNSS network engine became BNC's first and foremost ability.
     907<p>
     908With the advent of Ntrip as open streaming standard, BKG's interest turned towards taking advantage from free real-time access to GNSS observations. NGOs such as the IAG Reference Frame Sub Commissions for Africa (AFREF), Asia & Pacific (APREF), Europe (EUREF), North America (NAREF) Latin America & Caribbean (SIRGAS), and the International GNSS Service (IGS) maintain continental or even global GNSS networks with the majority of modern receivers supporting Ntrip stream upload. Through operating BKG's NtripCaster software, these networks became extremely valuable sources of real-time GNSS information.  In 2005 this was the starting point for developing the 'BKG Ntrip Client' (BNC) as a multi-stream Open Source NtripClient which allows pulling hundreds of streams simultaneously from any number of NtripCaster installations world-wide. Decoding incoming RTCM streams and output observations epoch by epoch through IP port to feed a real-time GNSS network engine became BNC's first and foremost ability. Converting RTCM streams to high-rate RINEX files to assist near real-time applications became a welcome by-product right from the start of this development.
     909</p>
     910<p>
     911For debugging real-time software some post processing capability is quite advantageous. So within time certain real-time options of BNC had to be complemented to work offline with reading data from files. Moreover, beginning 2012 the software was extended to support Galileo, BeiDou, and QZSS besides GPS and GLONASS. With that the Open Source tool BNC could be used for RINEX Version 3 file editing, concatenation and quality check, a functionallity not really covered at that time by UNAVCO's famous TEQC program because of its focus on GPS.
    913912</p>
    914913
     
    44834482[Add] String for Operating System in logfile output<br>
    44844483[Add] Full integration of 'rtcm3torinex'<br>
    4485 [Add] Extended command lile help<br>
     4484[Add] Extended command line help<br>
    44864485</td>
    44874486</tr>
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