Code tracking architecture influence on GPS carrier multipath

It is well known that carrier-phase multipath is one of the limiting error sources in high-precision differential GPS (Global Positioning System) applications. A thorough understanding of carrier-phase multipath is the first step in the course of mitigating its impact in high precision applications. Complete characterization of carrier-phase multipath error requires a fundamental theoretical description and mathematical modeling. However, the theory and models must be validated with real data. This paper documents the results of a study of the influence of GPS receiver code tracking architecture (coherent and noncoherent) on the carrier-phase multipath error, and provides a thorough validation of carrier-phase multipath theory. Validation is carried out for wide and narrow correlator spacing within coherent and noncoherent code tracking architectures by comparing bench test data to theoretical predictions. Prior to this effort, scant attention had been given to validating carrier-phase multipath theory against GPS data (Townsend et al., 1995). In addition, data collected for non-zero multipath phase rates is presented. The impact of GPS receiver architecture on the mitigation of phase-rate multipath was discussed.