Detail from satellite imagery supplied by the EROS Data Center
The United States Geological Survey (USGS) collects and makes freely available a vast array of earth sciences data that range from aerial photography to satellite imagery, digitized maps to digital elevation models of areas around the globe. The data are available through the USGS Earth Resources Observation and Science (EROS) Center.
Use the Find Data page for access to specific data types, such as land cover data, as well as data discovery tools like EarthExplorer, which allows for combined text and geographic searching. Other search portals are linked from this site as well.
Users are required to register in order to download data. Search results are presented from a variety of sources, depending on the resources sought. Large satellite images and other large files can incur long wait times for downloading, but all data are free and available for reuse.