Imagery: Free Sources and Directories

• ESDI (Earth Science Data Interface) at the University of Maryland GLCF (Global Land Cover Facility)
  • great map interface for finding imagery
  • includes LandSat7 imagery (coverage shown to the right)
  • each LS band is a separate 8-bit TIF file, so you can (must) assemble them yourself into RGB images
• MODIS Rapid Response System
  • provides true-color, 250m images of large parts of the world
  • JPEG files, with world files, mostly in Sinusoidal projection
  • though the focus of this site is on fires and other atmospheric issues, they nonetheless serve up an amazing amount of beautiful cloud-free coverage, such as the entire countries of Korea and Tibet
  • although the files works reasonably well with the assumption they are in normal Sinusoidal projection, they are reportedly actually in a special "Integerized Sinusoidal" (ISIN) projection
  • ISIN is not supported by most software, so they provide the free MODIS Reprojection Tool to project the data to other, well-known projections
  • the Visible Earth: MODIS page also has a set of imagery, but it is not as extensive or useful
• JPL OnEarth Global Mosaic
  • a server using the WMS protocol to serve combinations of all nine spectral bands of Landsat7 data
  • includes a very nice 15m true-color pan-merge layer, which has reasonable image quality, although it suffers from the usual problem of LandSat bands which have not been individually color-balanced, as well as cloud cover
  • you can use their simple web-based browser, but since it is WMS, you can also use any WMS-enabled client such as World Wind for a more powerful browsing experience
• DigitalGlobe
  • Although DG is a commercial imagery vendor, they have program called Point of Interest which provides free access to a 10 sq. km. area to US and Canadian governmental agencies (Non-Defense)
• OpenAerialMap
  • An open collection of aerial photographs, collected into a single coherent view of the world, served with a WMS.  You can upload your own imagery.
• NASA ESAD - Earth Science Applications Directorate
  • ESAD article at Terrainmap.com shows how to get free false-color imagery from their MrSID browser
  • in fact, this is an excellent source of LandSat5 (1990) data for the entire globe
  • it is not true-color or cloud-free
• USGS DOQ and NAPP
  • see aerial imagery page for a description of these USA-only datasets
  • Because DOQ is public-domain, you can get it from many places.  See the National Map Distribution System described on the page Getting USGS Data.
• USDA-NRCS Geospatial Data Gateway
  • uses a Java-based map interface to allow selecting a geographic area, display of (US Federal data) layers available, then FTP download or CDROM/DVD delivery
  • includes a great deal of CIR (Color Infrared) aerial photos which are otherwise spread out on servers in individual states
• NGA Raster Roam
  • when you can't find any imagery for some part of the northern hemisphere, try this NGA server which might have old 10 meter Digital Orthorectified Imagery (DOI 10) of your area
• ISS EarthKAM Datasystem
  • has visible-spectrum images taken from the International Space Station
  • see EarthKAM article at Terrainmap.com for more information
• earthinfo
  • a free, useful website which provides online geographic browsing, with links to both government and commercial sites which can provide access to imagery
• Global Land 1-KM AVHRR Project (Advanced Very High Resolution Radiometer)
  • the data is rough, low-quality - but coverage is global
• The JPL image archive's Mission to Planet Earth
  • has some high-res false-color (SIR-C/X-SAR) images
  • includes good images of the great wall of china, central Italy, parts of the bay area, and parts of Hawai‘i
• ResMap
  • although ResMap is a commercial company, you can browse their extensive imagery online and download (most of) the layers for free
  • see their instructions page
• NASA Ames
  • has a large collection of visible-spectrum images taken from the shuttle, but nearly all of them are low-contrast, clouded and oblique
• NASA Image eXchange (NIX)
  • overview of issues with NIX (it's very hit-and-miss)
• GeoGratis
  • a Canadian website that offers LandSat coverage for all of Canada and for part of the northern United States
• Cryptome Eyeball Series
  • a large set of high-resolution aerials of locations with some political significance; they are reportedly from the USGS, possibly via the National Map

Commercial sources and vendors (large list)