以DWG数字地图为例,研究如何快速准确获取数字地图中的居民地(房屋)注记.居民地注记属于点状要素,且一般位于居民地内部.根据这一特点,自动获取居民地注记的关键就是判断注记属于哪个多边形.对传统射线法进行改进,提出了去除顶点交点法判断点在多边形内外算法,并在某市数字地图数据入库中得到了应用,结果表明,该算法可行有效.
Digital maps are still the main data sources of GIS. How to transfer digital maps to GIS spatial database according to GIS data model is the key issue in GIS applications development. Map annotation is the important source to GIS spatial database. Taking the DWG formatted digital map as a sample, this paper conducts a research on how to obtain residential area annotations quickly and accurately. Residential area annotations belong to point features, and the key to obtain them is to determine each annotation contained in which residential area (polygon). One improved algorithm removing vertex typed intersection point is put forward. The performance of the algorithm is tested in some city digital map transferring to GIS database system. Experimental results show that the algorithm is feasible and efficient.