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Satellite Imagery

• NASA's Tutorial is a friendly introduction to satellite imagery (gentle enough for children)
• LandSat
  • LandSat is the name of a series of US imagery satellites.  The most commonly encountered data is from LandSat 4/5 or LandSat 7 (the latest).
  • the data was collected with US taxpayer money, so the raw data is in the public domain
  • however, you generally still have to pay someone to process the images (color-correct, merge, and improve georegistration) which typically costs $400 to $2000 per "scene"
  • each scene (image) is around 80 km on an edge
  • see Terrainmap.com article on LandSat 7 Satellite Imagery
  • each of the LandSat raw images has 8 bands, a lot more than just RGB:
    • "LandSat bands 3, 2, and 1 are the red, green, and blue reflected light. Assigning bands 3,2,1 to color channels red, green, and blue produces a "natural color composite" very similar to what you might see if you were flying over an area in an airplane."
  • LandSat7 bands:
    • Band 1      0.45-0.52      Blue-Green
    • Band 2      0.53-0.61      Green (often mapped to Blue)
    • Band 3      0.63-0.69      Red (often mapped to Green)
    • Band 4      0.75-0.90      Near IR (often mapped to Red)
    • Band 5      1.55-1.75      Mid-IR
    • Band 6      10.4-12.5      Thermal IR
    • Band 7      2.09-2.35      Short Wave IR
    • Band 8      0.52-0.90      Panchromatic
  • if you need to determine what LandSat scene is at a particular location, there are Shapefiles available from the GLCF: WRS2 is the "world reference system" used for LandSat 5-7
• ASTER
  • launched by NASA with international partners, since 2000 ASTER provides free or low-cost imagery (as well as elevation!)
  • the 14 bands vary from 15m to 90m resolution, each scene is 60 x 60 km
  • note that compared to LandSat7, there are no bands which map well onto RGB visible light, though an article on terrainmap.com says that reasonable results may still be possible
• MODIS [site down on 05.08.12]
  • The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument, was launched on the Terra platform December 1999; the second instrument on the Aqua platform May 2002
  • it is well-designed to capture visible light at moderate spatial resolution (250m –1km), to detect a large ranger of phenomena, and has near daily global coverage
  • some data is available online, see Free Sources of Imagery
• IKONOS
  • Space Imaging IKONOS satellite is the world's first commercial 1-meter remote sensing satellite
  • reportedly, "Space Imaging has made available for free download a sizable database of satellite imagery for the United States and for International locations"
  • see Commercial sources for how to buy IKONOS images, and the other commercial imagery vendors
• Alex's Remote Sensing Imagery Summary Table (ARSIST) was a list as of 2004 of the status, capabilities and availability of data from the most important satellite sources (around 30)

Processing Satellite Images