The application of zero phase filter on BDS geostationary satellite code multipath mitigation

Multipath delay is one of major error sources which limit global navigation satellite system (GNSS) positioning accuracy. Duo to the orbit characteristics, multipath effects on the code observables of geostationary earth orbit (GEO) satellites are more evident and can be tracked continuously over long time scales. We introduce a data processing technique, based on residual analysis, zero-phase filter and sidereal filtering, for mitigating the multipath effects on code rang measurement of GEO satellites, and investigate the characteristics of multipath series both in time and frequency domain. Since the multipath series have different frequency components, zero-phase filter is employed to decompose the low frequency components of multipath series with no phase shifting and distortion, and then the extracted multipath terms are applied as reference to correct the multipath effects on code observables of the subsequent day. A real data experiment shows that 33~64% improvement can be achieved in standard deviation of code measurement residuals, and the standard deviations of east, north and up components of single point positioning (SPP) accuracy are approximately reduced by 0.3m, 0.5m and 0.6m.