Detection of drainage channel networks on digitalsatellite

We present a technique for automatic detection of drainage channel networks on digital images acquired by conventional satellites such as LANDSAT and SPOT. Since these satellites are sun{synchronous, the approximate local sun angle at time of image acquisition is always known. Consequently, the spatial behavior of shading with respect to channels and other topo-morphologic features is known. This knowledge has been used to advantage in this work. We use a multilevel knowledge{based approach for this detection process. The rst and lowest level deals with image processing: radiometric and edge enhancement, edge detection and consolidation, and skeletonization; resulting in a complex network of Author to whom correspondence should be addressed. 2 lines. The second (intermediate) level of knowledge for network extraction performs a categorization of line segments in order of resemblance to channel elements on the basis of the strength and local disposition of shading about them. The highest level of knowledge that has been applied, reconstructs the channel network from a selection of these line segments based on structural considerations, including connectivity and streammow direction. This last stage of network extraction conforms naturally to a global view of a network. The extracted networks are smooth and appreciably connected and seem to be quite encouraging for developing this approach into practical uses.