Research and Implementation of Contours Automatic Generalization Constrained by Terrain Line

Generalization is the key method of map-scale transformation. Because Contour curve is complex and the topography characteristics are expressed in groups, the result of its generalization directly decides the map quality. For Douglas Algorithms can easily lead to memory overflow when recursion depth is too deep, the two-stack Douglas algorithm is used to extract the feature points from the contours. The reference threshold of the Algorithms key parameter is test and 2 m is selected as the optimal threshold. The terrain lines are automatically recognized and tracked by limiting the angle, which is formed by the three nearest points on the same contour. The contour clusters are automatically generalized under constraint with the terrain lines. The results indicated that the original surface topography was better retained when the terrain feature lines are used to constrain the contour automatic generalization.