An improved integrated generalization method for contours and Rivers using importance sequence of all points from these two elements

The existing integrated generalization method for contours and rivers using a 3D Douglas-Peucker algorithm is somewhat inefficient because it reserves points by constantly setting thresholds for exploring which one is suitable for the target scale. Here, we present an improved integrated generalization method for contours and rivers by applying an importance sequence scheme upon all points from these two elements. Our key method is an improvement upon the point selection using the 3D Douglas-Peucker algorithm. At first, no points were deleted, and the importance of all points from contours and rivers with geometric and semantic weights were calculated. Then, an importance sequence was formed which ordered all points from the largest to the smallest importance values. Finally, we adjusted the location of quantiles to reserve the necessary points for target scales. Results show that the proposed method can avoid the spatial and semantic conflicts between contours and rivers, and improve the cartographic generalization efficiency.