Processing system of degital elevation data for geomorphological research

为了使地理调查所编制的《数字国土信息》中的数字高程模型在地貌研究中得到应用，讨论了以下步骤和算法。1)全国DEM数据采集；2)DEM编辑；3)无高程数据的栅格和内河水面高程估算。4)网格孔径变化，5)局部地貌特征计算，6)小四边形统计参数计算，7)面状统计参数计算，5，6)DEM等高线划分，9)水系组成和流域面积计算。10)数字高程模型的显示与输出。以下程序也作为附加功能。A)栅格地图的变换，B)栅格等高线的绘制，C)不规则间隔数据的等高线绘制，D)DEM与卫星图像叠加的仿射变换，E)立体对的变换，F)卫星图像的显示。由于DEM大文件的快速I/O，本系统的程序主要用C语言编写，但在图形方面也用BASIC编程。

In order for Digital Eleveation Model in "Digital National Land Information" prepared by Geographical Survey Institute, to be useful in geomorphological study, following procedures and algorithms were discussed. And a processing system of DEM was built using a personal computer and peripherals.1) data acquisition from the national DEM, 2) editing for DEM, 3) elevation estimation for data failure grids and inland water surace without elevation data. 4) change of grid aperture, 5) calculation of local geomorphological characteristics, 6) calculation of statistic parameters in small quadrangle, 7) calculation of areal statistics of parameters of baove items 5 and 6. 8) contouring of DEM, 9) composition of drainage system and calculation of drainage area. 10) display and output of DEM.Following procedures ate also treated as additional functions.A) transformation to shaded raster map, B) raster contouring, C) contouring of irregularly spaced data, D) Affin transformation of DEM for overlay to satellite image, E) transformation of stereo pair, F) display of satelite image.The programs of the system are coded mainly in C by reason of rapid I/O of the large files of DEM, but BASIC is also used for coveniences in graphics.