The Recognition and Extraction of Hatched Polygons on Maps
地图上街区式居民地的识别与提取

It is indispensable to acquire geographic information from the existed topographical maps with various scales in the process of establishing geographic information system. The hatched polygons, which represent residential areas, are one of the most important sorts of map information. The strategies and algorithms of recognizing and extracting hatched polygons based on scanned map images are put forward and discussed. The RLS transformations in four directions for segmenting the hatched polygons are developed and realized. In addition, the algorithms for image transformations such as shrink, expansion, thinning, open graph deletion and hatched polygon recognition are also discussed in detail. Experiments show that recognition rate is about 96 percent with the methods developed in this paper.