Snow Depth Retrieval Using Ku-Band Interferometric Synthetic Aperture Radar (InSAR)

Monitoring seasonal snow accumulation is important as a factor required for evaluation of snow models, short- and long-term snowcover monitoring, and for both military and civilian operations, to include; hydrological planning (flood prediction), trafficability, avalanche control, and climatological/numerical weather prediction. Improved spatial analysis of snow depth and volume can help decision makers plan for future events and mitigate risk. The use of remote sensing tools provides a way of covering large areas that are difficult to measure directly using other methods. The Naval Postgraduate School (NPS) is using Interferometric Synthetic Aperture Radar (InSAR) to explore snow depth estimation approaches. Digital elevation models (DEMs) are produced during “Snow-off” and "Snow-on" conditions utilizing interferometric methods applied to airborne Ku-band Lynx SAR data acquired on a General Atomics Aeronautical, King Air aircraft. Multi-pass Single Look Complex (SLC) SAR data are spatially coregistered, SAR interferograms are produced to determine total wrapped phase, the wrapped interferograms are unwrapped, a flat earth correction is applied, and phase is converted to absolute height. Determination of the snow-off and snow-on DEMs and subsequent subtraction provides an estimate of elevation change caused by snow accumulation for specific locations and an integrated snow volume over a specified area. Manual snow depth measurements and snow analysis are being utilized to validate the SAR results in terms of snow depth, water content, and potential snow penetration. Current participants in the research include, the Naval Postgraduate School, Sandia National Laboratory, General Atomics Aeronautical, The Cold Regions Research and Engineering Laboratory US Army Research and Development Center (CRREL), and Mammoth Mountain California Ski Patrol. Cooperative research is also underway with the German Aerospace Center (DLR) utilizing their X-band SAR satellites (TerraSAR-X/Tandem-X). NPS is exploring future efforts utilizing a single-pass Ka-Band pass airborne system. The ultimate goal is to design operational approaches for regional snow depth determination using airborne and satellite SAR systems.