DEM (digital elevation model) is the abbreviation of digital elevation model, which is an important original data for watershed terrain and feature recognition. The principle of DEM is to divide the watershed into M rows and N columns of quadrilateral (cell), calculate the average elevation of each quadrilateral, and then store the elevation in a two-dimensional matrix. Because DEM data can reflect the local terrain features of a certain resolution, a large number of surface morphology information can be extracted by DEM, which includes the slope, slope direction and the relationship between cells. At the same time, the surface water flow path, river network and watershed boundary can be determined by certain algorithm. Therefore, to extract basin features from DEM, a good basin structure model is the premise and key of the design algorithm.

Data include:

1: 1km basic DEM

Data from 1:250000 contours and elevation points in China, including DEM, mountain shadow, slope and aspect map

2、SRTM 1km DEM

SRTM data cut from 1km around the world, including DEM, mountain shadow, slope and aspect map

3、Aster GDEM

Splicing, cutting and resampling to 1km according to 30m aster GDEM

The file format is: geotif

Dataset projection:

Projection = Albers Conical Equal Area",

GEOGCS["Krasovsky",

DATUM["Krasovsky", SPHEROID["Krasovsky",6378245,298.3000003760163]],

PRIMEM["Greenwich",0],

UNIT["degree",0.0174532925199433]],

PROJECTION["Albers_Conic_Equal_Area"],

PARAMETER["standard_parallel_1",25],

PARAMETER["standard_parallel_2",47],

PARAMETER["latitude_of_center",0],

PARAMETER["longitude_of_center",105],

PARAMETER["false_easting",0],

PARAMETER["false_northing",0],

UNIT["metre",1,]