Research On Contour Lines Automatic Extraction And Reconstruction Of Color Topographic Maps

Geographic resources digitization is a key factor for promoting the steady development ofgeographic information systems, and the acquisition of contour line is the most crucial step ofit. The study of the contour line automatic extraction and vectorization involves several areas,such as computer graphics, Engineering Graphics, artificial intelligence and so on, but thereare still some urgent problems. Some problems of contour lines extraction and reconstructionof color topographic maps are studied. Main contributions of the dissertation include:1. Taking into account the advantages of the threshold segmentation algorithm, a methodinvolving KFCM and threshold segmentation based on the HSI color space is proposed. First,a new image is constructed with the saturation value and spatial information of the map.Second, this new image is segmented by the Kernel Fuzzy C-Means Clustering method, andthen the threshold is calculated with the result obtained by the KFCM method. Third, we getthe whole contour line by segmenting the image with the threshold. Finally, severalexperiments are made to verify the validity of this method for several images with differentsaturation distribution.2. Min pair of breakpoints method cannot process the big gaps and easily cause falseconnection among the parallel lines. To solve these problems, an efficient approach to solvethis problem is proposed in this paper. A new calculation method of orientation difference isintroduced to solve the false connection among the parallel lines, broken points are dividedinto three types according to their feature，and then different connection strategy for each typebreakpoint is respectively implemented．And the connection process is carried out iterativelymany times，so that the big gaps of contour lines can be effectively connected．Thecomparative experimental results show that breakpoint connection performance and accuracy have be improved by the proposed approach．3. Combined with the thinning needs and the vector workflow of contour lines, someimportant methods are implemented and compared. We developed a simple experimentalsystem, which provided several functions about the aspects of the contour line vectorization: contour line extraction, skeleton extraction, breakpoint connection and contour linevectorization.