地形坡向生成的等高线束矢量合成法

利用地图数据库系统中的精确开窗功能,将所研究地区作适宜密度的网格开窗,形成独立的基于网格单元的等高线束,以此为基础信息源计算地形网格单元的坡向。其基本原理是矢量合成,当把每个矢量都用坐标表示后,窗口中的每条等高线的总方向归结为等高线各条边的矢量合成,坐标差的加法(第1次矢量合成);而小窗口地形的总体坡向则表现为各条等高线总体方向的矢量合成(第2次矢量合成)。由于等高线的疏密程度不同,网格系统中不可避免地有空值网格的存在,故需要研究坡向矢量的内插问题,此问题的解决是使用空值网格周边非空值网格作矢量合成(第3次矢量合成)。由于在整个过程的三个主要阶段中,使用同一种算法(矢量合成法),故本方法具有最简洁性。

Aspect Generation by Vector Composition of Contour Bunches

Using the database windowing functions the dense grids containing a bunch contour lines within them can be generated.The grid bunches of contour lines are independent from all neighbor grids,therefore,they can serve as the basis for deriving the aspect vectors.The basic principle lies in simple vector composition.After the representing of vector into coordinates,the general direction of every contour line can be seen as the composition of all of its vectors(line segments): sum of coordinate differences(the first vector composition).Further more,the grid terrain aspect can be calculated as the vector sum of all contour lines within the grid(the second vector composition).Because the density of contour line can differ from one place to another,it is unavoidable existence of empty grids which causes the necessity to research the appropriate method for aspect interpolation(the third vector composition).Due to the using of same method of vector composition in entire process of aspect calculation,therefore,the method proposed in this paper can be considered as the simplest one.