GIS中面积偏差控制下的矢量数据压缩算法

地理信息系统对矢量数据进行处理和应用的过程中,数据压缩是一个必须解决的问题,而通常采用的两种经典曲线数据压缩法:垂距限值法和道格拉斯-普克算法,都存在线段空间偏移过大以及面积偏差不可控的问题。利用曲线空间直线拟合的方法对曲线段中心轴进行空间逼近,通过增加面积偏差限值,提出了面积偏差控制下的矢量数据压缩算法,并以上海市崇明县岛屿边界轮廓矢量为例对该算法进行了验证。试验表明该方法对于解决两种经典压缩算法线段空间偏移过大以及面积偏差不可控的问题效果明显。

A New Algorithm of Vector Date Compression Based On the Tolerance of Area Error in GIS

In GIS,vector data is the most commonly used data structure.Data compression is an issue in vector data processing and applications.In this paper,several commonly used algorithms of vector data compression are analyzed and a new efficient algorithm is proposed to resolve the problems of the classic algorithms.The Douglas-Peucker algorithm and the vertical distance tolerance algorithm are commonly used algorithms in vector data compression.The Douglas-Peucker algorithm have the advantage that it has invariance in translation and rotation,but at the same time the result has a big area error and there is a contradiction between the compression ratio and retention of feature points for the curvature change.The advantages of the vertical distance tolerance algorithm is fast,but the area error and the characteristics of the retention curve space are very poor.In this paper,a new algorithm is proposed which improved vertical distance tolerance algorithm and resolved the shortcomings of the Douglas-Peucker algorithm and the vertical distance tolerance algorithm.The basic idea of the new algorithm is based on the vertical distance tolerance algorithm which increase an area error tolerance by adopting the method of straight line fitting to approximate the axis of the polyline in order to resolve the problem of the area error and declination of segment in space.An experiment is included,which verified the new algorithm is efficient by the example of dealing with the boundary contour vector of Chongming Island,Shanghai.In the experiment,the new algorithm has only 1 km2 error,but the classic algorithms has 6 km2 of the error.The most advantage of the new algorithms is that the area error can be controlled in a specified range.The experiments show that comparing with the two classic algorithms,the new algorithm has no substantial advantage in the compression ratio,but greatly improved the performance of two targets,area error and declination of segment in space.It proved that the new algorithm is efficient in the data procession which has high requirement in area accuracy and spatial characteristics such as the use of land resources.