Changeset 7594 in ntrip


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Timestamp:
Dec 1, 2015, 3:32:12 PM (7 years ago)
Author:
weber
Message:

Documentation completed

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1 edited

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  • trunk/BNC/src/bnchelp.html

    r7591 r7594  
    1919&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 1.5.1 <a href=#introManage>Management</a><br>
    2020&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 1.5.2 <a href=#introExamples>Examples</a><br>
    21 &nbsp; &nbsp; &nbsp; 1.6 <a href=#introLimit>Limitations</a><br><br>
     21&nbsp; &nbsp; &nbsp; 1.6 <a href=#introLimit>Limitations</a><br>
     22&nbsp; &nbsp; &nbsp; 1.7 <a href=#introLBack>Looking Back</a><br><br>
    2223<b>2.</b> <a href=#optsettings><b>Settings Details</b></a><br><br>
    2324&nbsp; &nbsp; &nbsp; 2.1 <a href=#topmenu><b>Top Menu Bar</b></a><br>
     
    871872</ul>
    872873
     874<p><h4>1.7 <a name="introLBack">Looking Back</h4></p>
     875
     876<p>
     877The obvious nucleus 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 (see 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 their locations.
     878</p>
     879
     880<p>
     881To 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 GNSS data called 'Networked Transport of RTCM via Internet Protocol' (Ntrip). The protocol was build on top of the HTTP standard and included the provision of meta data describing the stream contents. Any stream could now been transmitted world-wide 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 (see 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 them from there in support of a rover receiver. (Note that from a socket-programmers perspective NtripServer and NtripClient both act as clients; only the NtripCaster operates as a 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 of course again as Open Source under GPL.
     882</p>
     883
     884<p>
     885For 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' (see 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 precise real-time GNSS positioning through RTK networks. Thousands of reference stations upload observations via NtripServer to central computing facilities for any kind of precise real-time GNSS NtripClient application. In 2007 'Ntrip Version 2' has been released 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.
     886</p>
     887
     888<p>
     889With the advent of Ntrip as streaming standard, BKG's interest turned towards taking advantage from free standardized real-time access to GNSS observations. NGOs such as the Reference Frame Sub Commission for Europe (EUREF) 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 network 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 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 in order to feed a connected real-time GNSS network engine became BNC's first ability.
     890</p>
     891
    873892<p><h3>2. <a name="optsettings">Settings Details</h3></p>
    874893<p>
     
    49544973<tr><td>Estey, Louis H. and Charles M. Meertens</td><td>TEQC: The Multi-Purpose Toolkit for GPS/GLONASS Data, GPS Solutions, Vol. 3, No. 1, pp. 42-49, 1999.</td></tr>
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     4975<tr><td>Rupprecht, Wolfgang</td><td>DGPS-IP, <u>http://www.wsrcc.com/wolfgang/gps/dgps-ip.html</u>, 2000.</td></tr>
     4976
    49564977<tr><td>Weber, G., D. Dettmering and H. Gebhard</td><td>Networked Transport of RTCM via Internet Protocol (NTRIP). In: Sanso F. (Ed.): A Window on the Future, Proceedings of the IAG General Assembly, Sapporo, Japan, 2003, Springer Verlag, Symposia Series, Vol. 128, p. 60-64, 2005.</td></tr>
    49574978
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