GPS L1 Carrier Phase Double Difference Solution Using Low Cost Receivers

Stefan Söderholm

Abstract:	Positioning using GPS L1 and L2 carrier phase data is common practice today in geodesy. Often the objective is to measure one local baseline vector utilizing two highend GPS receivers. The equipment required for this is, however, very expensive. The development of low cost small form factor GPS L1 receivers have come to a point where good quality carrier phase measurements is available and double differencing systems utilizing these receivers have proven feasible. With inexpensive receivers like this high relative accuracy can become accessible to everyone. It also makes it feasible to build network of receivers that can measure not one, but even tens of local vectors at the same time. We will show that it is possible to measure short baseline vectors with centimeter level accuracy using GPS receivers targeted for mass-market applications. We will present data from a zero baseline test and short baseline tests, ranging form 1 meter to 20 km, using low cost GPS antennas and from a dynamic test utilizing a GPS signal simulator. The limiting factors for the position accuracy is such a system are the measurement noise, local errors like multipath, antenna phase center errors and errors in the integer ambiguities. For baselines > 10 km the atmospheric effects become the dominant source of error. If low cost receivers are used it is much more feasible to build a network of receivers were each receivers would transmit measurement data over a wireless link to the reference station that would calculate the local vector to each receiver. The number of possible applications for such a network includes monitoring containers in large storage areas, automatic machine guidance, measuring the deformation of high buildings and bridges, attitude measurements for airplanes, ships and cars as well as games and sports, i.e. football.
Published in:	Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005) September 13 - 16, 2005 Long Beach Convention Center Long Beach, CA
Pages:	376 - 380
Cite this article:	Söderholm, Stefan, "GPS L1 Carrier Phase Double Difference Solution Using Low Cost Receivers," Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005), Long Beach, CA, September 2005, pp. 376-380.
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