基于专题分类图的栅格矢量数据转换

A Algorithm for the Extraction of Polygonal Representation from a Thematic Classification Map

地理信息系统(Geographic Information System,简称GIS)中数据结构主要有两种:矢量数据和栅格数据。二者在原理上彼此独立,应用于不同的处理过程。例如美国环境系统研究所研制的ARC/INFO地理信息系统是一个典型的矢量数据结构的GIS,美国陆军工程兵团研制的GRASS是一个基于栅格数据的GIS。

A simple and improved algorithm is developed which extracts the polygonal contour representation from a raster format thematic classification map. The design adopts a 2×2 window which is used to scan and extract the boundary pixels of adjacent polygons along each pair of lines of the map. Contours are thus generated as a list of (X, Y) coordinate pairs, together with the attributes of the left and right regions at both sides of the boundary point. In the process of line segment tracking and polygon tracking, various attributes and topological relations are established. The structure, attribute and topological information of the vector data obtained are integrated and standardized, and they are easy to inquire and operate, and make the postprocessing flexible. The algorithm described in this paper has been implemented on a 386 microcomputer.