Gis Buffer And Overlay Analysis

Spatial analysis is one of several important functions in geographical information system (GIS). With the enrichment of spatial data and the improvement of capability to deal with them, people request better spatial analysis methods. This paper mainly does some researches on overlay analysis and buffer analysis which are important in spatial analysis.Buffer analysis is one of the several important spatial analysis functions of GIS. Buffer creation can be divided into three types: for points, lines and polygons, the buffer creation for lines is the key and basis, the procedure of the buffer creation for lines is divided into two steps: independently creating the buffer for each lines and merging the buffers created in the previous step. This paper presents and realizes a new kind of buffer radius-rotation creation algorithm based on angular bisectrix algorithm and circular arc algorithm. In addition, some specific cases are resolved during the procedure of the buffer creation, and recursion method is adopted to manage and store the self-intersected polygons of the buffer's borderline.Overlay analysis is a widely used spatial operation for the needs of spatial analysis in GIS. Because of large amount of spatial data in this operation, it is a critical technique about how to realize spatial overlay analysis very quickly with higher accuracy. In this paper, a kind of corresponding optimal algorithm for polygon overlay which can processes simple polygon and complex polygon on the basis of Weiler algorithm and Greiner-HorMann algorithm is presented and realized. This algorithm reduces the times that the vertex lists are traversed and consumed time of computing intersection point, in which the singly linked lists as the data structure is used to restructure the result polygons, so less memory space and running time are required. In order to avoid unnecessary intersecting operation, the judgement is adopted before computering intersection point and it reduces the time complexity.