Estimation of Lake Heights from Sentinel-3 Sar Mode Through Numerical Simulations

Altimetry missions provide very valuable measurements on hydrological bodies, although they have initially been built for ocean topography. The extension of their acquisition modes provides tens of thousands of lake and river observations thanks to recent OLTC table upgrades. The inversion of the waveforms is yet tricky because of mixed soil/water response, highly variable dynamics and surface roughness variations. In this paper, a physical retracking based on a priori simulation is proposed for Water Surface Height (WSH) estimation over lakes. The method is applied on Sentinel-3 SAR data. The results are illustrated and discussed over the Constance lake which is covered by three S3 tracks. Consistent estimations are obtained between the three with an unbiased RMSE better than 6cm. Extensive validation over Swiss lakes (19 tracks) has also been made leading to a median unbiased RMSE of 6cm.