Lake Level and Surface Topography Measured With Spaceborne GNSS-Reflectometry From CYGNSS Mission: Example for the Lake Qinghai

Abstract

This paper demonstrates inland water altimetry of spaceborne Global Navigation Satellite System-Reflectometry (GNSS-R) using the Cyclone GNSS (CYGNSS) mission data. From 12 tracks of raw data overpassing the Lake Qinghai, the bistatic group delay and carrier phase delay are extracted from the quasi-specular GNSS reflections. The water levels derived from the group delay observations are consistent with the Cryosat-2 and in situ gauge measurements. The surface topography profiles from the phase delay measurements show good self-consistence along the coincident tracks. Decimeter-level surface height anomalies are resolved with the phase delay measurements, which can be associated with the accuracy degradation of the geoid model in this region. Systematic errors remain in both group delay and phase delay altimetry measurements, which are attributed to the receiver orbit errors and ionospheric correction residuals. These limitations can be eliminated in further GNSS-R missions dedicated to altimetry applications.