Objectives Most of the existing building simplification methods focus on one or two aspects of the three principles: Area preservation, shape characteristics enhancement and drawing rectangles if possible. In practice, map generalization is a process of mutual restriction and trade-off of various influencing conditions, cartographic experts consider all the three aspects and balance them to reach reasonable results, sometimes they delete the small details on building's outlines, but it results in the area difference, sometimes they displace some points of the edges so that the area stays unchanged, but the vertices' location changes. It depends on the short-edge structures and distributions. By imitating this thinking and operation process of cartographers, a method based on short-edge structure recognition and progressive simplification is proposed.
Methods Firstly, the building outline is preprocessed. Then the contour segments are grouped, and the edge structure is identified and analyzed. After this, some specific situations are analyzed in detail, and the calculation region (the sequence of vertices associated with the simplification of a set of edges less than the tolerance) is used to determine the optimal simplification method. Lastly, the area difference is distributed to the whole building so that the building's area difference is reduced while the shape is maintained.OpenStreetMap (OSM) buildings are selected in the experiment.
Results Experimental results show that the proposed method can effectively reduce the number of graphic vertices, enhances the shape characteristics like parallel, right angle, etc. Also, the approach can control the area differences after generalization.
Conclusions The proposed method gives consideration to three aspects of the building simplification principles and balances them, which provides a new way for building simplification.