Advanced contour reconnection in scanned topographic maps

This paper presents an advanced reconnection of contour lines extracted from scanned topographic maps. In other words, this paper refers to the problem of gap filling. New properties such as 1) controlling a search mask for even number end points, 2) using the parabolic directions, and 3) back tracing less than ten pixels are added to the classical semi-automatic method to improve performance and accuracy. Proposed method has been applied to many different maps and the results of two implementations are given in this paper. An analysis and comparison of obtained results show that proposed method improves run time and accuracy about 22-44% and 12-14%, respectively.