ASTER Global Digital Elevation Model (ASTER GDEM) is a global digital elevation data product jointly released by National Aeronautics and Space Administration (NASA) and Japan's Ministry of Economy, Trade and Industry (METI) .The DEM data is based on the observation results of the new generation of Earth observation satellite TERRA Completed, it is produced by 1.3 million stereo pair data collected by ASTER (Advanced Space borne Thermal Emission and Reflection Radio meter) sensors, and its coverage area exceeds 99% of the earth's land surface. The data has a horizontal accuracy of 30 meters (95% confidence) and an elevation accuracy of 20 meters (95% confidence). This data is the third global elevation data, which is a significant improvement over the previous SRTM3 DEM and GTOPO30 data. ASTER GDEM released two versions. The first version was released in June 2009 and the second version was released in October 2011. Compared with the first version, the second version has make further progress in water coverage and deviation removal. The quality of the data has been greatly improved. This dataset is the second version of the ASTER GDEM dataset in the Shule River Basin, including DEM, mountain shadow, slope, and aspect data. Spatial resolution: 1 radian second (about 30 meters), accuracy: vertical accuracy of 20 meters, horizontal accuracy of 30 meters.
A total of 137 soil samples of different vegetation types, different altitudes and different terrains were collected from June 2012 to August 2012. The soil layer of each sample point was divided into three layers of 0-10cm, 10-20cm and 20-30cm, with an altitude of 2700-3500m m. The vegetation types were divided into five types: Picea crassifolia forest, Sabina przewalskii, subalpine scrub meadow, grassland and dry grassland. At the same time of sampling, hand-held GPS is used to record the location information and environmental information of each sampling point, including longitude, latitude, altitude, slope, aspect, terrain curvature, vegetation type, soil thickness, maximum root depth, etc. Soil bulk density: The measurement method of soil bulk density is to put the sample into an envelope and dry it in an oven at 105℃ for 24 hours, then take it out and place it for 30 minutes to weigh. The ratio of the weighing result to the volume of the ring cutter is the soil bulk density, and the unit is g/cm3. Soil mechanical composition: hydrometer method is used to measure the soil mechanical composition, which includes the content of soil sand, silt and clay.
DEM is the English abbreviation of Digital Elevation Model, which is the important original data of watershed topography and feature recognition.DEM is based on the principle that the watershed is divided into cells of m rows and n columns, the average elevation of each quadrilateral is calculated, and then the elevation is stored in a two-dimensional matrix.Since DEM data can reflect local topographic features with a certain resolution, a large amount of surface morphology information can be extracted through DEM, which includes slope, slope direction and relationship between cells of watershed grid cells, etc..At the same time, the surface flow path, river network and watershed boundary can be determined according to certain algorithm.Therefore, to extract watershed features from DEM, a good watershed structure pattern is the premise and key of the design algorithm. Elevation data map 1km data formed according to 1:250,000 contour lines and elevation points in China, including DEM, hillshade, Slope and Aspect maps. Data set projection: Two projection methods: Equal Area projection Albers Conical Equal Area (105, 25, 47) Geodetic coordinates WGS84 coordinate system
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LinksNational Tibetan Plateau Data Center