Contour Line Extraction from Paper-based Topographic Maps

Abstract

Contour line is the main linear feature on topographic maps. Extraction of contour lines is tedious and \u00a0time-consuming \u00a0process, \u00a0and \u00a0is \u00a0still \u00a0an \u00a0interesting \u00a0problem. \u00a0A \u00a0novel \u00a0method \u00a0for \u00a0extraction \u00a0of \u00a0contour lines from paper-based topographic maps is presented in this paper. In our approach, we firstly segment color topographic \u00a0maps \u00a0for \u00a0achieving \u00a0the \u00a0binary \u00a0image \u00a0of \u00a0brown \u00a0color \u00a0contour \u00a0lines. \u00a0Then, \u00a0mathematic morphology method is used to filter the binary image. Next, Utilizing c-means algorithm to look for initial seed \u00a0point \u00a0on \u00a0thinning \u00a0contour \u00a0lines. \u00a0Fourthly, \u00a0utilizing \u00a0improved \u00a0active \u00a0contour \u00a0model \u00a0to \u00a0extract \u00a0non- thinning \u00a0contour \u00a0lines. \u00a0Last, \u00a0we have \u00a0analyzed \u00a0the \u00a0directional \u00a0field \u00a0of \u00a0contour \u00a0lines near the \u00a0gap, \u00a0and \u00a0then reconnected \u00a0broken \u00a0contour lines. \u00a0The performance \u00a0of \u00a0the algorithm \u00a0is tested \u00a0on \u00a0several \u00a0topographic maps and comparing with other algorithms.