As the Global Positioning System (GPS) has matured over the last decade, expectations regarding system performance have grown steadily. This has placed pressure on receiver manufacturers and system providers to be ever more creative in their efforts to mitigate error sources. Historically, multipath has been the dominant error source in differential GPS (DGPS). However, with the recent decision to deactivate Selective Availability, multipath has become a significant error source for all GPS users. In 1991, the narrow correlator was introduced to the market and was shown to reduce multipath errors by as much as 90% over conventional receivers. Over the past several years, a number of multipath-mitigation techniques have been developed and promoted. This paper will explore the theory behind each technique and will provide a performance comparison. The inherent assumptions and limitations of each technique will be discussed as well.
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