方向关系在地理信息系统（GIS）中占据着十分重要的地位，由于它的模糊性和依赖空间实体形状的特性，使得它的形式化描述和判断比较困难。本文在三角形模型（CDR）方法的基础上，利用最小矩形（MBR）四边的Voronoi多边形及其边界，形式化描述了方向关系，进而将方向关系分为主方向关系和次方向关系，并分别给出了两者利用MBR四边Voronoi多边形及其边界判断的算法。

Directional relation is very important in GIS,but because of depending on the size of objects,it is difficult to make a formal description and determination. In this paper on the basis of CDR,a solution using Voronoi Region of MBR is suggested,and the wonderful results have been acquired.