DNESYS-an expert system for automatic extraction of drainage networks from digital elevation data

The problems that arose in earlier programs to map drainage systems are analyzed in detail. An expert system called the drainage Network Extraction System (DNESYS) is described. It uses both local operator and global reasoning to extract drainage networks and ridge lines. A stream representation called a parameterized directed graph (PDG) is constructed to model a drainage system. The construction of the model begins with an initial pixel labeling procedure. Then, a network tracing and property measurement procedure converts the two-dimensional low-level labeling information into a symbolic database for high-level processing. The application of Dempster-Shafer evidence theory allows evidence collection and uncertain reasoning to be performed against the DNESYS knowledge-base that contains the drainage system model and the organized expert knowledge. By discarding erroneous information and supplying missing information, DNESYS produces a complete PDG which can be converted into the final drainage system