GTOPO30 is a digital elevation model for the world, developed by United States Geological Survey (USGS).
It has a 30-arc second resolution (approximately 1 km), [1] and is split into 33 tiles stored in the USGS DEM file format.
According to DTED and USGS DEM the absolute vertical accuracy of GTOP30 varies from ±30 meters.
[2] This map is derived from GTOPO30 data that describes the elevation of Earth's terrain at intervals of 30 arcseconds (approximately 1 km).
It uses hypsometric tints instead of contour lines to indicate elevation.