The Alaska DEM project: repeat-geometry approach for generating accurate InSAR DEMs

In recent years the rapidly growing field of SAR interferometry (InSAR) has showed its potential to provide high quality three-dimensional information in the form of digital elevation models (DEMs). Especially during the ERS tandem mission, a large number of valuable data sets were acquired. The Alaska DEM project was initiated to demonstrate the capability of SAR interferometric data to meet the topographic needs of the State of Alaska. For the high-priority areas identified by the Department of Natural Resources, a large number of data sets from the ERS tandem mission are available providing multiple coverage of the same area in ascending and descending orbits. A processing strategy for calculating the most accurate result in this repeat geometry has been developed. An iterative approach processing image pairs from the smallest to the longest baseline is used to obtain higher accurately InSAR DEMs. A statistical evaluation of results helps to identify and to remove outliers before the individual results are mosaicked together in a final result. Layover and shadow masks are derived from orbital data to identify areas of poor data quality. For quality control the results are compared to high-resolution airborne data and a point target analysis for corner reflectors is carried out. The paper describes the processing strategy in detail and shows examples of one of the high-priority areas.