A Novel GNSS Precise Point Positioning Method Based on Spherical Harmonic Expansion

Abstract

ABSTRACT The Global Navigation Satellite System (GNSS) precise point positioning (PPP) from carrier-phase data is influenced by complex elements. The error sources are divided into two categories according to their relation to the signal propagation path. A new GNSS PPP algorithm based on spherical harmonic expansion (PPP-SH) is proposed, which expresses the error adjustments related to the signal propagation path through the spherical harmonic expansion, such as high-order ionosphere delay, zenith wet delay, phase wind-up delay, multipath delay and so on. Carrier-phase data of multiple continuous epochs are used to achieve the sequential sliding PPP solution, and the truncated singular value decomposition and iteration method by correcting characteristic values are used to solve the ill-conditioned equations in the PPP-SH algorithm. The reliable results can be obtained by using dual-frequency ionospheric-free carrier phase data when spherical harmonic expanding to degree 5. The standard deviations of E, N and U are 0.48, 0.43 and 0.27 cm, respectively. The addition of velocity parameters has positive influence on accuracy of positioning. The best positioning results are obtained by using the precise ephemeris and precise clock bias provided by ESA and the standard deviations of E, N and U are 0.41, 0.43 and 0.26 cm, respectively.