Multiresolutional characterization and mitigation of GNSS signal for robust positioning

While the use of wavelet filtering on applications such as audio and video is known, in this research. wavelet filters are applied as a practical tool to improve positioning accuracy of a navigatioll-grade receiver in challenging environments. A single, stationary recel\,'er operating OIl the L1 frequency, and collecting data in 15-minute segments, was used to obtain pseudoranges which were then used to compute positions. The magnitudes of these pseudoranges are often overstated due to multipath. ~Iultipath mitigation was applied tothese signals using a hvo-stage wavelet filter. The first stage operates in the pseudorange domain to remove bias error and the second stage operates in the position domain to minimize the effect of the low velocities that existed among the stationary positions. This filtering had a marked effect of reducing positioning scatter (variance). To measure the effect of this filtering, several statistical moments (before and after filtering), were compared. Throughout datasets studied, the unfiltered position scatters tend to be markedly non-Gaussian showing extreme effects of skew and kurtosis in addition to high variance. The position scatters after filtering tend to be highly Gaussian with far lower degrees of skew and kurtosis. In this study, the results obtained from the data sets sho'Ned significant improvement, less than 1.5 m with a probability of 96.5%, in standard deviation of the estimated positions.,