CryoSat-2 SARIn Interferometric Processing for DEM Generation

The SAR/interferometric radar altimeter (SIARL) on the CryoSat-2 platform is designed to accurately determine the height changes in the Earth's continental and marine ice fields. In addition, its synthetic aperture radar interferometry mode (SARIn) is capable of providing precise three-dimensional measurements. However, SARIn level 2 products provided by the European Space Agency (ESA) do not fully utilize interferometric information. In this paper, the basic principles of the SARIn mode are introduced. By integrating the traditional interferometric synthetic aperture radar (InSAR) technique, a processing scheme is proposed for SARIn level 1b (L1b) data to extract digital elevation models (DEMs). This processing scheme uncludes three steps. Firstly, checking the quality of the input data eliminates erroneous information. Secondly, a starting point for phase unwrapping is determined, based on the magnitude and the coherence of the received signals and a targeted algorithm is accirdingly designed and implemented to unwrap the interferometric phase along the across-track direction on a line-by-line basis. Thirdly, the look angle of the satellite is calculated and used to estimate the 3D information of ground points. After a process of interpolation, DEM are generated. With the use of the proposed scheme, the SARIn L1b data acquired between January 2012 and April 2012 were processed. The ground elevation of Lambert Glacier in Antarctic was mapped and compared to the ICESat DEM and RAMP DEM. The results demonstrate that a DEM generated based on SARIn data can satisfy the research requirements for ice cap mapping in polar areas.