Practical Evaluation of RTCM Network RTK Messages in the SWEPOS™ Network

Dan Norin, Gunnar Hedling, Daniel Johansson, Soren Persson, Mikael Lilje

Abstract:	Permanent reference stations for GNSS have for a long time been used for positioning of rovers in RTK mode. The RTCM format for transmission of observation data has made it easier to use a variety of GNSS receiver brands. Ten years ago, work was begun to develop RTCM messages that would contain compressed observation data or models describing the observations from a network of several permanent reference stations. It was self-evident that these RTCM messages should primarily be formed for broadcasting. At the same time server-based systems were developed, where the RTK rovers are sending their positions via NMEA GGA and in return receive synthetic observations from a fictitious reference station. This concept proved to be very efficient and robust, much to the surprise of many people in the surveying and positioning community. Test measurements with RTK rovers have been performed with the RTCM Network RTK messages 1014, 1015 and 1016 in a 14 station sub-net of the SWEPOS™ network. SWEPOS is the Swedish national network of permanent reference stations for GNSS. The Network RTK server was running Trimble GPSNet and as rovers Trimble R8 and Leica GX1230 receivers have been used. Solutions with Network RTK messages in both static broadcast mode and automatic mode have been compared with standard Virtual Reference Station solutions. The results from the measurements showed that there were no obvious differences in accuracy between Network RTK messages and Virtual Reference Station solutions. The obtained horizontal accuracies expressed as RMS values of the distribution around the true positions were in the order of 14 millimetres. The differences between static broadcast and automatic mode were also unnoticeable. Concerning the initialization periods for the ambiguity fixed solutions, they were slightly longer for Network RTK messages than for Virtual Reference Station solutions. Suitable applications for the use of Network RTK with RTCM Network RTK messages are also discussed.
Published in:	Proceedings of the 2009 International Technical Meeting of The Institute of Navigation January 26 - 28, 2009 Disney's Paradise Pier Hotel Anaheim, CA
Pages:	353 - 359
Cite this article:	Norin, Dan, Hedling, Gunnar, Johansson, Daniel, Persson, Soren, Lilje, Mikael, "Practical Evaluation of RTCM Network RTK Messages in the SWEPOS™ Network," Proceedings of the 2009 International Technical Meeting of The Institute of Navigation, Anaheim, CA, January 2009, pp. 353-359.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In