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)