Source: USGS NED 1/3 at Seamless data distribution system
Source for USA and Mexico: USGS NED 1 at Seamless data distribution system
Source for Northern Canada and void filling: Natural Resources Canada CDED at Geobase
Main source: Shuttle Radar Topography Mission (SRTM) data products
Source for Alaska: USGS Alasaka NED 2 at Seamless data distribution system
Source for North of Canada: Natural Resources Canada CDED at Geobase
Source for North of Eurasia and Groendland: Viewfinder Panoramas
Source for Antartica at Radarsat Antarctic Mapping Project
Source of SRTM Void filled for Eurasia: Viewfinder Panoramas
Seamless data distribution system
Source USA: NLCD 2006 Seamless data distribution system
Source Canada: Natural Resources Canada Circa 2000 at Geobase
Source Europe: Corine landcover at European Environment Agency
Source World: Globcover at European Environment Agency