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NGS Real Time Network Status & Future Prospects

Explore the latest developments in real-time network status and future possibilities within the NGS framework. Learn about CORS site modifications, GPS receiver data transmission over the Internet, standardized protocols, and software design issues.

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NGS Real Time Network Status & Future Prospects

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  1. NGS Real Time Network Status & Future Prospects Neil Weston NGS Convocation, 2005 Silver Spring, MD

  2. Main Concepts • Modify CORS sites for real time data transmission • GPS receiver data • Transmission via the Internet • Standardized protocols and formats • Not a navigation service!

  3. CORS Site Modification • Receiver modifications • Firmware • Multiple satellite systems • Data interval • Communications / Network modifications • Routers • Increased bandwidth • Internet • Software

  4. Network Design Issues • What format? • What stations? • What software? • What distance? • What data rate? • What latency?

  5. Formats • RTCM-SC104 • Versions – 2.0, 2.1, 2.2, 3.0 • Type 1 Fixed GPS corrections (1 sec) • Type 3 GPS reference station parameters (10) • Type 16 GPS special message (30,60) • Type 18 RTK uncorrected carrier phases (1) • Type 19 RTK uncorrected pseudoranges (1) • Type 22 Extended station parameters (15) • Type 59 Proprietary messages (1)

  6. Formats cont. • Raw • Topcon/Javad Compact (1) • Ashtech MBEN (5) / PBEN (5) / SNAV • Thales ASCII • SP3 ASCII • Trimble RT17, concise • Leica LB2 • RINEX • BINEX

  7. CORS Stations • NDGPS • WAAS • PBO Network • Other contributors sites

  8. Software • NTRIP - Networked Transport of RTCM via Internet Protocol (version 1.5) • NTRIP is an RTCM standard • Application-level protocol streaming Global Navigation Satellite System (GNSS) data over the Internet • Based on hypertext transfer protocol (HTTP/1.1) • Simultaneous connections from PC’s, laptops, receivers to a broadcast host • Streams data to stationary and mobile users

  9. Software cont. • NTRIP – Three major components • NtripClients – acts as an HTTP client • NtripServers – acts as an HTTP client • NtripCasters – HTTP server

  10. DGPS/ RTK Data Rates • DGPS – 0.5 kbits/sec • RTK – 5 kbits/sec • Much less demanding than Internet radio, teleconferencing … 128 kbits/sec …

  11. Administration of NtripCaster • Logs • Sourcetable • Configuration file • User registration

  12. NTRIP Pros / Cons • RTCM standard • Open documentation • Software components developed under GNU General Public License • Communications through a HTTP port • Workload on server side • Not supported by mobile IP provider

  13. Data Rate / Latency • Modified CORS Stations – 1 second interval • Latency – Not more than 1 to 2 seconds • Most third party software packages buffer the data before processing begins

  14. NTRIP Consequences • Easy to become a provider • Drivers available for real time software development • End of special hardware for receiving RTCM / RTCA • Support for networking software • Lots of potential for mass-usage • Sites, networks and coverage will grow • Many third party client and server applications already exist

  15. NTRIP Demonstrations www.euref-ip.net:2101 • RTK station • RINEX test station • Erlanger alt.ngs.noaa.gov:2101 • NGS_GRD • NGS_LAB How you can listen

  16. Conclusion • Streaming GNSS data over the Internet is feasible • No significant lack of performance compared to other transportation media • Advantages for user / service providers • Developments for various products • Promising solution for GIS • Faster data access

  17. References • NTRIP BKG – GPS/GLONASS Data Center • http://igs.ifag.de/index_ntrip.htm • RTCM – Radio Technical Commission for Maritime Services • http://www.rtcm.org

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