Contour Line Extraction from Paper-based Topographic Maps

Contour line is the main linear feature on topographic maps. Extraction of contour lines is tedious and time-consuming process, and is still an interesting problem. A novel method for extraction of contour lines from paper-based topographic maps is presented in this paper. In our approach, we firstly segment color topographic maps for achieving the binary image of brown color contour lines. Then, mathematic morphology method is used to filter the binary image. Next, Utilizing c-means algorithm to look for initial seed point on thinning contour lines. Fourthly, utilizing improved active contour model to extract nonthinning contour lines. Last, we have analyzed the directional field of contour lines near the gap, and then reconnected broken contour lines. The performance of the algorithm is tested on several topographic maps and comparing with other algorithms.