Abstract
It has been strongly requested to get automatically a precise digital elevation model from a topographic contour image. But, because of overlapping other symbols, the image usually includes many broken contours. To connect these correctly, a global restoration technique considering states of adjacent contours is needed. In this paper we propose a new global restoration method using an extended Voronoi diagram that produces a relationship graph of adjacent contours. Based on an idea of reference contours, it determines pairs of broken contours to be connected and interpolates their gaps with spline curves. It can satisfactorily restore broken contours that have been considered difficult to connect.
