Detection of Multipath Influence at DGPS Reference Stations

Marc Hoper, Thomas Boelow and Harald Hoffmann

Abstract:	The disturbance of GPS measurements caused by multipath influence is known as a major source of error in current GPS applications and limits the availability of a carrier phase solution. Different approaches are already available to minimize this influence. Until one of these approaches leads to a product that is available at a reasonable price, multipath will keep disturbing the user’s position. To enhance the navigation system’s integrity, the receiver autonomous integrity monitoring (RAIM) is used. But it can usually identify only one disturbed satellite. The possibility of detecting signals influenced by multipath only by inspecting range and carrier phase measurements of the satellites would further increase the integrity of GPS based navigation systems. Knowledge about the signal’s multipath disturbance for each channel would allow identifying and excluding more than one influenced satellite if there are no other constraints, like GDOP. During the research a method was found that extracts an indication value for the magnitude of multipath influence based on the receiver’s raw data. This value can be calculated online for each visible satellite and refers to a previously defined time window. The algorithm mainly uses code phase information and thus is not applicable for carrier phase multipath detection. This method was developed to increase the integrity and availability of a GPS carrier phase solution, which is needed for flight inspections purposes. This paper deals with this detection of multipath influence at DGPS reference stations, which means for stationary applications, and provides an overview about the concept of the detector.
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	581 - 590
Cite this article:	Hoper, Marc, Boelow, Thomas, Hoffmann, Harald, "Detection of Multipath Influence at DGPS Reference Stations," Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001), Salt Lake City, UT, September 2001, pp. 581-590.
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