the differential method for the mechanic movement analysis is proposed in this paper. with the method, only the displacement vector polygon of a mechanism is needed to be established.
at the same time the author points out that the polygon vertexes can be sorted clockwise or anticlockwise by judging the sign of the vector polygon area.
同时指出可以通过判断矢量多边形面积的正负值将多边形的顶点按照顺时针或逆时针方向排序。
for the sake of realizing some special functions in spatial analysis of gis, it is necessary to covert irregular vector polygon into regular grid.