EUREF Real Time - DGNSS over the Internet

With the increased capacity of the Internet, applications that transfer continuous data streams by IP-packages, such as Internet Radio, have become well-established services. Compared to these applications, the bandwidth required for the transmission of real-time GNSS data is relatively small. Consequently, the IAG Sub-commission for Europe EUREF decided to set up and maintain a differential GNSS infrastructure (DGNSS) on the Internet using stations of its European GPS/GLONASS Permanent Network EPN (see Resolution #3, 2002). The objective is to disseminate RTCM corrections over the Internet in real-time for precise differential positioning and navigation purposes. This has been investigated first by W. Rupprecht in 1999.

EUREF-IP

The acronym for these activities is EUREF-IP (IP for Internet Protocol). DGNSS trial servers currently provide RTCM corrections as generated in a number of countries. You may download free RTCM client software (Euref-ip-rtcm, Version 1.0) to access the appropriate data stream for your positioning or navigation application. Please read the client instructions for further details and links to other client programs. EUREF-IP aims to meet the growing need for Europe-wide improved real-time determination of coordinates. It makes use of recent developments in the interconnection of mobile communication and the Internet. GPRS-based data transfer using PDAs is among the promising techniques for real-time access to both geo-information (GIS) and geo-referencing (RTCM) data using the same communication channels.

The Network

As of June 2002, DGPS trial servers providing RTCM corrections over the Internet are available from reference stations of the following institutions:

· Bundesamt für Kartographie und Geodaesie, Frankfurt, Deutschland

· Università di Cagliari, Facolta di Ingegneria, Dipartimento di Ingegneria Strutturale, Sezione di Topografia, Cagliari, Itala

· Institut Cartografic de Catalunya, Barcelona, Espana

· Universita degli Studi di Padova, Dipartimento di Geologia, Paleontologia e Geofisica, Padova, Itala

· Bundesamt für Landestopographie, Abteilung Geodaesie, Sektion Geodaetische Grundlagen, Wabern, Schweiz

Additional stations from the European Permanent Network are expected to become involved soon. Receiving RTCM corrections from this real-time network enables the determination of coordinates referred to the European Terrestrial Reference System ETRS89.

Future Developments

Today’s trial software is based on a plain Serial-to-TCP conversion of streaming data on the reference-side (server) and TCP-to-Serial re-conversion on the rover-side (client). Conventions on formats for a more sophisticated dissemination of RTCM corrections over the Internet do not exist. EUREF-IP intends to make new software available under the terms of the GNU General Public License. This software will include protocol definitions to transport RTCM corrections from servers via casters to clients. It will consider specifics of reference station networks, security and firewall issues, and massive simultaneous access in support of location-based services. The software will be available free of charge by the end of 2002. Because its functionality does not interfere with RTCM standards, it will simply replace today’s trial software. Please have a look at a EUREF presentation entitled Real Time Streaming of Differential GPS Corrections over the Internet (1.8 MB) for an explanation of background, the present situation, and plans.

Call for Participation

The real-time network providing RTCM corrections for Europe needs densification. Support is possible from any geodetic GNSS receiver continuously operated at a known position close to an Internet connection. The minimum requirements for participation in today’s EUREF-IP test phase are

- Operation of a GPS/GLONASS receiver with well known antenna position, capable of generating RTCM corrections,

- Operation of an Internet-connected PC next to the receiver, running a server program.

Feel free to download the server software (Euref-ip-dgps) if you are interested in supporting EUREF-IP. Read the server instructions for further details and links to other server programs. After setting up your server you need to announce its availability within the project. Please contact euref-ip@ifag.de for a registration.