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An overview of the Tri-Decadal Global Landsat Orthorectified mosaic data collections are derived from a global set of high-quality, relatively cloud-free orthorectified TM and ETM+ imagery from Landsat 4, 5 and 7.
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The Tri-Decadal Global Landsat TM Orthorectified and ETM+ Pan-sharpened Mosaics data collections are derived from a global set of high-quality, relatively cloud-free orthorectified TM and ETM+ imagery from Landsats 4, 5 and 7. This dataset was selected and generated through NASA's Commercial Remote Sensing Program, as part of a cooperative effort between NASA and the commercial remote sensing community to make available quality-screened, high-resolution satellite images with global coverage over the Earth's land masses. The data collection was compiled via NASA contract with Earth Satellite Corporation, now MDA Federal Inc. (MDA), (Rockville, MD) in association with NASA's Scientific Data Purchase program.
Ground control points are fixed, and images have been registered to the Universal Transverse Mercator (UTM) map projection and coordinate system and the World Geodetic System 1984 (WGS84) datum. All image bands have been individually resampled, using a nearest neighbor algorithm. Positional accuracy on the final image product has a Root Mean Square Error of better than 100 meters (MSS) and 50 meters (TM and ETM+). The Landsat data were acquired and processed through a National Aeronautics and Space Administration (NASA) contract with Earth Satellite Corporation, Rockville, Maryland, and are part of NASA's Scientific Data Purchase program.
When possible, data were collected when vegetation was at peak greenness. Peak greenness was determined from global 1-kilometer Advanced Very High-Resolution Radiometer (AVHRR) Normalized Difference Vegetation Index (NDVI) data. When peak greenness data were not available, images from other times of the year were substituted.
The collections are derived from approximately 7,461 TM (Landsat 4-5) images and approximately 8,500 ETM+ (Landsat 7) images, which were selected to provide a full set of global coverage (circa 1990 and circa 2000). All selected images are either cloud-free or contain minimal cloud cover. Only images with a high-quality ranking (based on the possible presence of errors such as missing scans or saturated bands) were selected.
The average acquisition date for the Tri-Decadal Global Landsat Orthorectified TM data is 1990 (+/- 3 years). However, individual scenes may range from 1985 to 1996. These Landsat data have been orthorectified, using geodetic and elevation control data to correct for positional accuracy and relief displacement. Large blocks of Landsat data were adjusted through a patented procedure using pixel correlation to acquire tie-points within the overlap area between adjacent Landsat images. The Landsat TM scenes were mosaicked by matching individual histograms and feathering overlapping areas together to create a TM Mosaic product. The mosaics are contrast enhanced color image data products comprised of Landsat TM bands 7, 4, 2 composited in red, green, and blue, respectively. The resulting mosaics are made up of several Landsat scenes covering a 5-degree (north-south) segment of a standard, 6-degrees (east-west), UTM partition. The Tri-Decadal Global Landsat Orthorectified TM Mosaic data collection consists of approximately 500 TM (Landsat 4-5) mosaics . Digital Object Identification (DOI): /10.5066/P91LYVCM
These data products consist of pan-sharpened versions of the ETM+ scenes. The pan-sharpening process involved a resolution merging process, which allows the fusion of the higher-resolution panchromatic band (8) with selected lower-resolution multispectral bands (7,4,2) to create a higher-resolution ("pan-sharpened") color image. The Tri-Decadal Global Landsat Orthorectified ETM+ Pan-sharpened Mosaic data collection consists of approximately approximately 2,600 ETM+ (Landsat 7) mosaics. Digital Object Identification (DOI): /10.5066/P9NRGYJ3
All Tri-Decadal Global Landsat Orthorectified data products have been pre-processed according to a standardized set of processing parameters.
Coverage Maps indicating the availability of TM Mosaics products are available for download.
Coverage Maps indicating the availability of ETM+ Pan-Sharpened Mosaics products are available for download.
Tri-Decadal Global Landsat Orthorectified TM and ETM+ Pan-sharpened Mosaic can be searched and downloaded from EarthExplorer. The collections are located under the Landsat Legacy category.
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The EarthExplorer (EE) user interface is an online search, discovery, and ordering tool developed by the United States Geological Survey (USGS). EE supports the searching of satellite, aircraft, and other remote sensing inventories through interactive and textual-based query capabilities.