Landsat
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Revision as of 12:14, 17 February 2007
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Landsat 7 is a satellite of the USGS Landsat Project. The satellite is equipped with an ETM+ instrument that is an eight-band multispectral scanning radiometer capable of providing moderate resolution image data of the Earth's surface.
The band information is combined to produce an image, and by using different bands you can get images that represent human eye perception, thermal, infrared or other visuals.
Landsat 7 data is available globally at a scale where you can pick out many prominent features in the landmass. The maximum resolution of the ETM+ is 15 meters per pixel on the panchromatic band.
Contents |
i-cubed
An Isilon cluster was used by i3 to optimally process the raw Landsat7 data using sophisticated i3 color-balancing algorithms. Isilon systems donated to NASA were again used to rapidly build the i3 donated color-balanced imagery into World Wind's tiling scheme. Much thanks goes to i3 and Isilon for their generosity of this imagery into the public domain.
Visible
- The maximum resolution is 15 m per pixel.
- Uses bands 3, 2, 1
NLT
NASA Learning Technologies has processed the Landsat 7 data to create their own imagery. Pan-sharpening the images was planned, however other priorities mean that 30 meters will be the maximum resolution for the forseeable future. See NLT Landsat Processing Techniques for information on how the data was processed, and NLT Data Issues for known issues.
Visible
- The maximum resolution is 30 m per pixel.
- Uses bands 3, 2, 1
Pseudo
- The maximum resolution is 30 m per pixel.
Geocover
Geocover is a product of MDA Federal (formerly EarthSat), and is pseudo color Landsat imagery. The 1990 data was acquired with Landsat 5, and the 2000 data with Landsat 7's ETM+.
2000
- The maximum resolution is 15 m per pixel.
- Uses bands 7, 4, 2
1990
- The maximum resolution is 30 m per pixel.
- Uses bands 7, 4, 2
OnEarth
OnEarth is a project of the NASA Jet Propulsion Laboratory.
Visible
- The maximum resolution is 15 m per pixel.
- Uses bands 3, 2, 1
Pseudo
- The maximum resolution is 15 m per pixel.
- Uses bands 5, 4, 2.
Data Acquisition
Landsat 7 only gets one chance every 16 days to cover any given area. If there are clouds, fog, smog, snow on the ground (too white), too much grass on the ground (too green), too low or too high sun angle (low contrast), satellite maintenance, solar storm, etc, that chance is lost. A few bad takes in a row, and a whole year is lost. A scene is 160x180km, and a perfect scene has to have perfect conditions for the whole area.
Landsat 7 was launched in 1999 and now it has some data quality problems. The U.S. government is currently working toward a Landsat Data Continuity Mission (LDCM), which will field a Landsat-like sensor on board the next-generation NOAA/DoD weather monitoring platform, or on-board a dedicated satellite.
The Landsat 7 data will be the best available global images for quite a while, and the fact that they are free and available on the net makes them even more significant.
External Links
- An Introductory Landsat Tutorial
- emporia.edu - has information about the bands
