An Improved Doppler-Aided Smoothing Code Algorithm for BeiDou-2/BeiDou-3 un-Geostationary Earth Orbit Satellites in Consideration of Satellite Code Bias

The extensive use of carrier-aided smoothing code (CSC) filters has led to a reduction in the noise level raw measurements GNSS positioning and navigation applications. However, existing CSC technique is sensitive changes integer ambiguity, then procedure needs be restarted presence cycle slips. As Doppler shift instantaneously observed immune slips, Doppler-aided (DSC) algorithm would more promising challenged environment. Based on Hatch filter, an optimal DSC approach proposed with principle minimum variance. Meanwhile, inhibit effect integral cumulative error Doppler, balance factor adopted adjust contributions DSC. observable not only affected by thermal noise, but also limited systematic bias. Satellite bias (SCB) was identified each frequency for BDS-2 satellite. By minimizing sum absolute value residuals, polynomial segment fitting as function elevation angles applied establish SCB correction model based epoch-differenced multipath (MP) deviations. Finally, different types experiments demonstrate validity efficiency refined filter corrections available BDS un-GEO satellites.