The U.S. Geological Survey (USGS) and the National Geospatial-Intelligence Agency (NGA) have released an updated and more accurate global elevation model that pulls data from Digital Terrain Elevation Data (DTED®) from the Shuttle Radar Topography Mission (SRTM); Canadian elevation data; SPOT 5 Reference 3D data; data from NASA’s Ice, Cloud, and land Elevation Satellite (ICESat); and updated Antarctica and Greenland terrain models.
This new elevation data called Global Multi-resolution Terrain Elevation Data 2010 (GMTED2010), replaces the thirty year old GTOPO30 terrain model.
GMTED2010 is a suite of seven raster data products: minimum elevation, maximum elevation, mean elevation, median elevation, standard deviation of elevation, systematic subsample, and breakline emphasis.
The spatial resolution of GMTED2010 ranges from 30, 15 and 7.5 arc-seconds (approximately 1 kilometer, 500 meters and 250 meters, respectively). The data was created by aggregating the highest resolution data available in a given geographic area. At this spatial resolution, the data can be appropriate for GIS analysis at the regional, continental, and global level.
GTOPO30 is georefenced to the World Geodetic System 1984 (WGS 84) horizontal datum and, in most cases, to the Earth Gravitational Model 1996 (EGM96) geoid as the vertical datum.
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More details about this global elevation data can be found at USGS Open File Report 2011-1073. The data can be accessed for free and without restriction from the USGS EROS center.
Exactness of a grid value should be as possible. I propose medium value for each cell. For deep water flows, reservoir, and depth in coastal zones they should be set (may be set) with ‘-(value)’. Possible format may be
10.3 or near.
If Really, spatial resolution of the grid must provide geomorphologic exactness (not more 15-10m) in view to perceive terraces, and be exact in calculation of water/sediment balances. 1 km is not convenient. It distorts water levels oscillations and is only rough approximation. However, for large river basins a grid size became too large for computing, for output, for data transfer, and etc. It is A task for future. about F10.3 (in meters).
Data input was used for 500×500 grids, what is almost upper limit for handle input. Should be written special tools for it.
What to do with precipitation, and air temperatures. Experienced were single gauges for each area.It required to correct basic data received by a gauge, corrected by elevation in each cell. For Precipitation was used local areas ( clouds) which should be moved above grid for more exactness… It is diffucult work, but very useful for results accuracy…
There are many others notes for each layer, but it should be done separately in dependence of content.