Geocoding for classification of ERS/JERS-1 SAR composites

Abstract

Using combined SAR image data acquired by the Japanese JERS-1 (L-band, hh-polarization) and the European ERS-1 (C-band, vv-polarization) yields excellent classification results. An important preprocessing step prior to classification is the geometric and radiometric calibration of the image data from each instrument. In order to match and radiometrically calibrate JERS-1 and ERS-1 radar images the geocoding of the scenes using terrain height information is indispensible. Therefore the generation of digital elevation models (DEM) and vector/point data for the search of ground control points is necessary. An invaluable data resource is made available on-line on the Internet through the US Geological Survey (USGS). Using DEM data, the sensor/target geometries are analyzed to derive the local incidence angle and determine layover and shadow regions from the DEM data. Layover and shadow regions need to be determined for both JERS-1 and ERS-1 scenes, and than excluded from the classification procedure. The radiometric information in both scenes needs to be calibrated using area correction terms derived from the local angle of incidence. This paper discusses the generation of DEM's from USGS data the generation of layover/shadow mask and local incidence angle maps, as well as the radiometric correction for ERS-1/JERS-1 SAR data at the University of Michigan.