The problem of automatic digitizing of contour maps is discussed. The structure of a general contour map is analyzed, and its topological properties are utilized in developing a new scanning algorithm. The problem of detection and recognition of contour lines is solved by a two color labeling method. It is shown that for maps containing normal contour lines only, it suffices to distinguish between so-called “even” and “odd” lines. The “tangency problem” involved in practical scanning is discussed, and a solution based on minimizing computer memory space and simplifying control program is suggested.
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