Technical Specifications:
World 1,000 Meter DEM
Operation
- The World database is comprised of the entire surface of the World at 1,000 meter resolution in seamless DEM format. The database equaling 3 Gigabytes of decompressed DEM Data, representing 933 million elevation points.
Resource Details
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GTOPO30 is a global digital elevation model (DEM) with a horizontal grid spacing of 30 arc seconds (approximately 1 kilometer). GTOPO30 was derived from several raster and vector sources of topographic information. GTOPO30 was completed in late 1996, developed over a three year period through a collaborative effort led by staff at the U.S. Geological Survey's EROS Data Center.
GTOPO30 is a global data set covering the full extent of latitude from 90 degrees south to 90 degrees north, and the full extent of longitude from 180 degrees west to 180 degrees east. The horizontal grid spacing is 30-arc seconds (0.008333333333333 degrees), resulting in a DEM having dimensions of 21,600 rows and 43,200 columns.
The horizontal coordinate system is decimal degrees of latitude and longitude referenced to WGS84. The vertical units represent elevation in meters above mean sea level. The elevation values range from -407 to 8,752 meters. In the DEM, ocean areas have been masked as "no data" and have been assigned a value of -9999. Lowland coastal areas have an elevation of at least 1 meter, so in the event that a user reassigns the ocean value from -9999 to 0 the land boundary portrayal will be maintained. Due to the nature of the raster structure of the DEM, small islands in the ocean less than approximately 1 square kilometer will not be represented.
Projection GEOGRAPHIC
Datum WGS84
Zunits METERS
Units DD
Spheroid WGS84
World DEM database coverage and rendered in a "Cartographic" style
Pricing
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