基于多边形单纯剖分的复杂地类图斑符号填充

A Map Symbol Filling Method for Complex Land Patch Based on Simplex Partition

地图符号配置对于表达地图内容、揭示空间规律具有重要作用。由于地理环境特征的差异性,土地利用数据中存在大量复杂地类图斑。传统方法对复杂地类图斑进行地图符号填充会出现部分区域符号布局不合理或无符号的问题,为此,该文提出了一种基于多边形单纯剖分的复杂地类图斑符号填充方法。首先对图斑多边形构建约束Delaunay三角网,将地类图斑剖分为单纯形;根据单纯形特征对Delaunay三角形分类,以提取多边形骨架线,作为地图符号填充位置;然后根据多边形几何特征与人类视觉认知规律制定了地图符号填充策略。运用全国第二次土地调查的地类图斑数据进行实验分析,并与ArcGIS软件的面状符号填充效果进行对比,结果表明,该文方法更适于复杂地类图斑的符号填充。

Filling map symbols in complex land patch may cause uneven distribution of symbols when using traditional filling method,which makes it difficult to express map content properly.To solve this problem,a method of symbol filling based on simplex partition was proposed in this paper.Firstly,the constrained Delaunay triangulation was constructed within a real object,which divided polygon into triangles.Secondly,the triangles were distinguished into three types according to the number of each triangle with neighbor triangles,and skeleton line was extracted from Delaunay TIN to be as the map symbols filling position.Thirdly,to divide simplex sequences into long and narrow parts and two-dimensional extension parts,the concept of triangle width was defined.If the average width of simplex sequence was less than width threshold,the simplex sequence would be partitioned from the polygon.Finally,for two kinds of simplex sequences,different symbol filling methods were used.Traditional filling method was used for two-dimensional extension parts,while for long and narrow parts,symbols were filled along the skeleton line at regular intervals.The experiment was conducted using the land patch data in the Second Land Investigation to verify the novel method.Compared with traditional method,the experimental results show that under different scales,the proposed approach enables uniform distribution of symbols in a polygon and benefits the accurate expression of map content.