尺度变化的土地利用类型数据的综合研究

利用不同尺度的土地利用类型数据,表达不同的内容、传递不同的信息,可揭示不同的现象与规律。宏观的大尺度数据通常是由较精细的小尺度数据经数据综合而得。在论述土地利用类型综合特点的基础上,提出由土地利用类型尺度上推引发的土地利用类型数据综合过程,并给出类型转换、同类图斑合并、小图斑取舍与处理、数据简化与拓扑关系维护的处理流程,在一定程度上解决了土地利用类型数据的尺度上推问题。重点论述构建小图斑的多边形骨架线并将其剖分、归并入相邻图斑的小图斑处理方法,提出基于Douglas-Peucker算法改进的构造平衡线的多边形简化方法,对土地利用类型图斑进行简化,使简化前后面积及拓扑保持一致。通过对实验结果的分析表明,该方法适合于土地利用类型数据的综合,并可作为其他GIS数据尺度上推的参考方法。

Research on Data Generalization of Land-use Types Caused by Type Up-scaling

Land-use type data at different scales expresses different content,transmits different information,and reveals different phenomena and laws.The macro-data at large-scale is usually generalized from many fine data at small-scale.The process of land-use type data generalization caused by type up-scaling was addressed and the methods of land-use type aggregating,merging of adjacent parcels with the same type,small parcels amalgamating,spatial-data simplifying and topology preserving are elaborated respectively.This paper focused in the approach of small polygon amalgamation by skeleton subdivision,which first used constrained Delaunay method to build triangulation network and used the triangulations to build the skeleton lines according to five different types of triangulation and then divided the small polygon using the skeleton lines into many smaller polygons adjacent to different polygons and merged them to the different adjacent polygons.Uses this approach to amalgamate the small parcels which their areas are smaller than criterion,the proportion of different land-use types was roughly the same as before amalgamation;then proposed a polygon simplification method to simplify land-use type polygons,which was based on the Douglas-Peucker algorithm and constructed a balanced line to preserve the same area as before simplification.In order to maintain the topology of the polygons,first divided the polygon into different polylines according to their adjacent relations and simplified them respectively and then rebuilt the polygon with the simplified polylines.The area preserved simplification process first used the Douglas-Peucker algorithm to simplify the polyline and got the smallest simplification unit and within the unit built a balance line to preserve the same area as before simplification.Thus the area and the topology before and after simplification are consistent.The results of the test data showed that the method is suitable for the generalization of land-use type data,and can be used else where when geospatial data were up-scaled.