Lessons learned from comparing gauge levels with Landsat and Radar Altimetry observations: Case-Study of Lake Nasser (Egypt)

Landsat imagery and satellite radar altimetry are combined in Lake Nasser over a period of several years. This fusion process provides several related products, including the estimation of water volume changes and bathymetry. The practical use of this multi-sensor approach requires a proper quantification of the error sources. In this work we use height measurements from an in situ gauge in order to study the relationship between areas measured by Landsat imagery and heights measured by radar altimetry. The joint usage of the various data sets is investigated and discussed. Radar altimetry heights compare well with in-situ data, apart from some discrepancies which are not fully explained. When related to Landsat-derived areas, the in situ data provide a tighter fit than radar altimetry data. The free availability of satellite data and the possibility to get two independent areal and height measurements from free satellite platforms, make the approach exposed here particularly attractive.