# Presentation: 933812

## NGS Real Time Network

- Status & Future Prospects

**Neil Weston**
**NGS Convocation, 2005**
**Silver Spring, MD**

## 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!

## CORS Site Modification

- Receiver modifications
- Firmware
- Multiple satellite systems
- Data interval
- Communications / Network modifications
- Routers
- Increased bandwidth
- Internet
- Software

## Network Design Issues

- What format?
- What stations?
- What software?
- What distance?
- What data rate?
- What latency?

## 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)

## Formats cont.

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

## CORS Stations

- NDGPS
- WAAS
- PBO Network
- Other contributors sites

## 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

## Software cont.

- NTRIP – Three major components
- NtripClients – acts as an HTTP client
- NtripServers – acts as an HTTP client
- NtripCasters – HTTP server

## Slide 10

## Slide 11

## DGPS/ RTK Data Rates

- DGPS – 0.5 kbits/sec
- RTK – 5 kbits/sec
- Much less demanding than Internet radio, teleconferencing ... 128 kbits/sec ...

## Administration of NtripCaster

- Logs
- Sourcetable
- Configuration file
- User registration

## 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

## 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

## 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

## NTRIP Demonstrations

- _[www.euref-ip.net:2101](http://www.euref-ip.net:2101/)__	__	_
- RTK station
- RINEX test station
- Erlanger
- _[alt.ngs.noaa.gov:2101](alt.ngs.noaa.gov:2101)_
- NGS_GRD
- NGS_LAB
- How you can listen

## 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

## 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