Abstract
The purpose of this report is to arrange the definitions of geomorphometric measures for digital ele-vation models (DEMs) and to prescribe some advanced applications of the 50 m-DEM newly deli-vered by the Geographical Survey Institute of Japan.
We express terrain surface morphology in the two forms of computer-compatible data structure. One is the vector type, in which the surface is defined as a set of local triangular patches, or contour lines. The other is the raster type as a two-dimensional array of even-spaced terrain heights (DEM). In the report we focus our interest on the geomorphometric measures for DEMs.
The measures can be classified into three types by localization of objects: point, window, and drain-age-basin. The window measures are statistical parameters of heights within the scanning window, and they are plotted at central points of the windows resulting in raster maps of geomorphometry.
To calculate drainage-basin measures it is necessary to prepare anteriorly the drainage direction matrix (DDM). The DDM is a raster map in which the drainage direction (related to the neighbor-ing lowest point) is indicated by the chain code of the rook's or queen's case. We are not concerned here with the interesting skill of automatic generation of DDM from DEM.
The drainage-basin measures are the same as the window measures in definition, but they are plot-ted at outlet points of the basins, and therefore resulted also in raster maps of basin geomorphome-try.
Newly defined measures in this report include projected area (A), surface area (AS), and volume (V) of topography defined within the window and the drainage basin, and their derivatives for ex-ample, general steepness (A/AS), general relief (V/A), and steepness index (V/A3/2).
