Automatic Extraction Of Contour Line In Color Scanned Map

Topographic contour line is one of the key tasks in GIS development. The automatic extraction of contour line from color scanned topographic map is one of the key techniques of geographic data attainment. This paper takes color map with a scale of 1:10000 as the research object and emphasizes on the recognition and acquisition of contour line.Main contributions of the dissertation include:1. A practical segmentation algorithm is presented directly based on HLS color model, in which space elements in map can be divided clearly.2. A method of map algebra can wipe off noise though expanding elements such as rivers, roads, annotations and so on.3. This paper introduces a method with which disconnected contour lines can be joined. First, I expand the counter lines so that closer lines can intersect. Second, the axes will be obtained from the expanded lines. The axes are shortened the distance between disconnected contour lines. The result is better than other ways.