International Wide Area Differential GPS Networks

Mohamed Abousalem, James McLellan, Ed Whatley, Paul Galyean

Abstract:	With the growing need for accurate, reliable, and couutry-wide low-cost DGPS coverage, there has been a signiticant movement towards the use of WADGPS systems worldwide. WADGPS integrates DGPS data from various widely separated reference stations where the redundancy of the data is the prime cause for the system accuracy and reliability. The integrated solution accounts for the spatial decorrelation of error sources at individual reference stations, and if one or more of the reference stations malfunction, the rest of the stations will still be available for generating accurate DGPS corrections. The user is therefore gnaranteed continuous, accurate and reliable DGPS service. In the United States, the ACCQPOINT WADGPS system has been developed to provide DGPS users across the country with DGPS corrections via FM subcarriers. The system will provide various positioning accuracy levels ranging from above 10 m to below 20 cm. The fmt phase of ACCQPOINT WADGPS system has been tested and results show that a one-to-five metre accuracy is achievable using DGPS corrections from 10 continental DGPS reference stations. Similar systems are being developed for other countries as well. Accordingly, ACCQPOINT Communications is currently developing a universal FM demodulator compatible with the MBS communications standard in North America and the RDS standard in Europe and other countries. The paper includes a description of the ACCQPOINT WADGPS system. Some test results are included to confirm the achievable positioning accuracies using GPS data collected from four different locations in the USA. Integrity monitoring results are also given for a 24-hour period of data collection in Calgary.
Published in:	Proceedings of the 1995 National Technical Meeting of The Institute of Navigation January 18 - 20, 1995 Disneyland Hotel Anaheim, CA
Pages:	371 - 379
Cite this article:	Abousalem, Mohamed, McLellan, James, Whatley, Ed, Galyean, Paul, "International Wide Area Differential GPS Networks," Proceedings of the 1995 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 1995, pp. 371-379.
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