Mapping ice sheet margins from ERs-1 SAR and spot imagery

We demonstrate a new technique to automatically map the margin of ice sheets using ERS-1 SAR and SPOT imagery. The technique relieson a series of image processing techniques including edge enhancement, dynamic thresholding, region growing, edge detection, and edge following. The mapping technique is used to measure temporal displacement of the ice sheet margin north and south of the Jakobshavn Glacier in Greenland. During the 4 year interval between 1988 and 1992 we find ice sheet margin advance/retreat rates of about ± 12m/year, consistent with independent observation. We combine the 1988 and 1992 data to assign an average ice margin location for the observation interval assuming a constant displacement rate. The resulting snapshot of the ice sheet margin can be used as a benchmark for future change detection studies. In both cases the uncertainties are better than 200m.