Image Gallery:  GeoCover Mosaic
(634 pixels x 654 pixels)
Source: This image was generated by the GeoCover project at Earth Satellite Corporation
under contract with the National Aeronautics and Space Administration (NASA).
Other GeoCover products are funded by the National Imagery and Mapping Agency (NIMA).

In 1998, NASA embarked on an effort to produce a set of high quality Landsat TM and MSS imagery covering the majority of the Earth's land surface – a digital map of the Earth – for three decades.  The resulting GeoCover program is now in the process of "painting" the most detailed map ever of the Earth’s terrestrial surface. 

The image above, showing the Central Asian Region of Afghanistan and Pakistan depicted in "true color," is a mosaic of Landsat Thematic Mapper images, and was constructed using 121 100x100 nautical mile scenes from around 2000. The Landsat Thematic Mapper is roughly equivalent to a 50 megapixel digital camera with very fine optical lenses that permit "digital photography" from space.

To construct the complete digital map of the Earth, the decade of the 80s is being mapped using the 80-meter resolution Landsat Multispectral Scanner, while the 90s decade and first decade of this century are being mapped using the 30-meter resolution Thematic Mapper. The Landsat scenes are specifically selected to minimize cloud cover so a clear view of the Earth’s terrestrial features is revealed. At the projects completion nearly 24,000 Landsat scenes will have been processed and made available to the public – over 20 terrabytes of data.

The GeoCover imagery is georeferenced to the Earth’s surface using control points derived from other U.S. satellite sources, producing a map of the terrestrial surfaces of the Earth called GeoCover-Ortho. Control points are used in conjunction with a sophisticated sensor geometry model and with the adjacent imagery to create an accurate spatial relationship between the raw Landsat imagery and the surface of the Earth – a positional accuracy estimated at 50 meters on average. The authors of the product suggest that the accuracy "is better than the vast majority of the world's 1:200,000 scale maps." Related efforts by the National Imagery and Mapping Agency are resulting in the production of categorized land cover versions of GeoCover-Ortho, called GeoCover-LC. This product provides labeling of each point of the Earth’s surface corresponding to one of thirteen land cover categories.

GeoCover is expected to be available for the entirety of the Earth’s surface within one year and represents a potential source of a historical baseline for land cover information. The data are being made available to the general public via Earth Satellite Corporation in Rockville, MD, and the Land Processes Distributed Active Archive Center at the USGS EROS Data Center in Sioux Falls, SD.

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