Extraction of bajadas from digital elevation models and satellite imagery

A methodology was designed for the extraction of bajadas from the 15 min US Geological Survey digital elevation models and Landsat Thematic Mapper ima gery. The method was demonstrated for the Death Valley-California where pro gressive eastward tilting has enabled the west-side fans to coalesce and fo rm bajadas. First, the drainage that crossed the uplands and the bajadas wa s extracted from the DEM. The drainage pixels were successively grown by ch ecking the surrounding pixels on the basis of their gradient. It was conclu ded that for gradient in the interval [2 degrees, 11 degrees] the upslope b ajadas border was segmented. In order to eliminate the drainage pixels that belonged to the uplands. the drainage pixels were subtracted. Then, the is olated small 8-connected foreground pixels were identified and subtracted t oo. Finally, region growing was performed again to the remaining pixels wit h the same growing criterion. Isolated 8-connected background pixels, repre senting almost flat regions inside bajadas, were identified and merged to t he segmented pixels. At the end, by taking into account the spectral respon se in the satellite image, the downslope border of bajadas was segmented. T he extracted polygon was in agreement with the information depicted on (a) the US Geological Survey topographic map of scale 1 : 100,000 and (b) the s atellite image and (c) the polygon classified manually by a photo-interpret er. (C) 2001 Elsevier Science Ltd. All rights reserved.