GIS Data Sources: Global

• Data by Country from DIVA-GIS contains common basemap layers. See DIVA-GIS's main data page for more international layers.
  Global Administrative Areas is a related site with several levels of admin. divisions, in several formats
• Global GIS DVD: Compiled by the USGS and the American Geological Institute; contains USGS and other public domain data, including global coverages at a nominal scale of 1:1 million in the following categories: Economic Structures, Environment, Gazeteers, Imagery, Land, Political, Rasters, Reference, Transportation, and Utilities.  Several formats, mostly shapefiles or rasters.
• VMAP Level 0 (formerly known as Digital Chart of the World)
  From the US National Geospatial-Intelligence Agency (NGA), providing about the level of detail found on 1:1,000,000 charts. Worldwide layers are divided into 4 parts as below. The files are tarred and gzipped.
  • Europe / Northern Asia / North America / South Asia / Australia / South America / Africa / Antarctica
  • The files are also available on CD-ROM in the Public Documents CD collection at call number D 5.358: VMAP 0
  These are in Vector Product Format (VPF); ArcGIS has an Import from VPF tool in its Coverage Toolbox.
  • The "GIS-Lab" site has VMAP0 files in shapefile format, as well as VMAP1 files (based on 1:250,000 charts) for some areas.
  • Vmap is the source of many free layers at sites such as DIVA-GIS.
• National Geospatial-Intelligence Agency (NGA) Country Files Tab-delimited text files of named features on U.S. military maps (approximately the features you'd find on a 1:250,000 scale map or chart).  Includes decimal latitude and longitude coordinates sometimes up to 6 places past the decimal. The file format page includes variable definitions.
• Natural Earth Public domain dataset, worldwide coverage at resolutations appropriate for 1:10m, 1:50m, and 1:110m scales.

Population

• LandScan Population raster layers at 1 km resolution, for 2000 through to last year. Online viewer, or can access from GIS software as WMS images or WCS raster layers. Duke users only.  NOTE for ArcGIS 10.2.x users: When adding a WCS or WMS connection from Add Data...GIS Servers, to gain access you must enter a single space in both the username and password and check the “save password” box in the Add Data dialog.

Climate, Environment, Human Impact

• UNEP GEO Data Portal From the UN Environment Programme. Files tagged "geospatial" will be rasters.  Most other files will be data in tabular format with a locational attribute (country name, etc.).
• FAO GeoNetwork Lots of geospatial data from the Food and Agriculture Organization of the UN.
• SEDAC (Socioeconomic Data and Applications Center) at CIESIN (Center for International Earth Science Information Network) at Columbia Univ.
• ESA-CCI (European Space Agency - Climate Change Initiative). Includes worldwide datasets, including aerosols, biomass, clouds, fires/burned areas, greenhouse gases, glaciers, Antarctic ice sheet, Greenland ice sheet, lakes, land cover, high res land cover, ocean color, ozone, permafrost, sea salinity, sea ice, sea level, sea temperature, snow, soil moisture, and more. To get the data, use the tools from the main data page. Has land cover data annually for 1992-2015 at 300 meter resolution with 38 categories of land cover.
• World Resources Institute (WRI) Maps & Data Use the Advanced Search to qualify your search. A wide variety of data, mostly relating to WRI projects around the world.
• GlobeLand30 (National Geomatics Center of China) Worldwide land cover data in 30-meter resolution raster files (GeoTIFF). Coded for ten broad classes of land cover.
• Global Forest Watch Data Sources page leads to datasets on many aspects of forests worldwide.  The organization also hosts some cloud-based GIS data via ArcGIS Online.
• Renewable Energy Data Explorer (REexplorer) Online mapping tool for visualizing energy-related map layers from selected non-US countries, most of which can be downloaded as GIS files.
• CGIAR-CSI Consortium for Spatial Information includes links to detailed SRTM elevation data and several climate datasets.
• Climate Hazards Center at UCSB  Their CHIRPS dataset includes worldwide rainfall data rasters at .05-degree resolution covering back to 1981, at detailed time intervals. Compiled from both remote sensing as well as station data.
• WorldClim - Global Climate Data Includes GIS raster layers in several resolutions representing global climate data normals based on 1950-2000 data. Also includes projections as well as paleoclimate reconstruction data.

Geology and Soils

• World Geologic Maps Mostly small-scale GIS data from the USGS, many deriving from their Open File Report series.
• ISRIC - World Soil Information Soil data from the International Soil Reference and Information Centre.
• Soil Geographic Databases  Maintained by David G. Rossiter, who "attempts to catalogue all freely-downloadable primary soils information usable in a GIS either as "point" observations, polygon maps, or gridded maps ("rasters")."

Marine Data

• Marineregions.org  Includes data and links to data such as EEZ (Exclusive Economic Zone) boundaries, ecosystems, gazetteers of names, and bathymetry.
• Global Marine Ecosystem Data from NCEAS (National Center for Ecological Analysis and Synthesis). Includes rasters of marine human impact data and ecosystem area data.
• GEBCO General Bathymatric Chart of the Ocean. Includes geospatial data such as bathymetry data, undersea feature names, and WMS services.