GIS中面的游程编码表达、实现与应用

游程编码是一种常用的压缩和表达栅格数据的技术,GIS中面状要素的栅格化有时也采用这种方法。本文主要研究面的游程栅格化方法,设计并实现了一种扫描线算法,主要思路为:计算扫描线与面边界的交点并组织为有序断点链表形式,然后根据扫描行上断点序号的奇偶性建立有序游程链表。为降低栅格化过程中位置精度的损失,提出用实数值记录游程边界的方法。论文还探讨了游程编码的常见操作及其实现,通过实例说明其在GIS面操作中的应用与优势。

Run-length encoding system about area: representation, implement and applications in GIS

Run-length encoding system(RLE) is a common technique of raster data compressing and expressing,it is used on occasion for area features rasterizing in GIS.Focused on the rasterizing method of area objects with RLE data structure,this paper improved an algorithm based on scan line theory,which includes 2 critical steps.Firstly,figure out all points of intersection between scanning line and area boundary curve,save these breakpoints in form of ordered linked list;Secondly,according to the parity of breakpoint sequence number in scanning line,to build up ordered run-length list.In order to reduce the loss of position accuracy in the process of rasterization,a method about run-length boundary recorded by real-value is introduced.In additional,this paper presented common operations of run-length encoding system,advantages and applications in GIS area operation are also illuminated by some examples.