High spatial resolution imagery from the Landsat satellites has provided us with the longest record of terrestrial observations since 1972. Recognizing the need to provide high-resolution satellite data to the scientific community, NASA's Commercial Remote Sensing Program Office has been working to assemble the first wall-to-wall global coverage of ortho-rectified Landsat Thematic Mapper and Multi Spectral Scanner data to support scientific studies. This database is expected to be of great value to researchers studying a variety of problems.
The need for high-resolution data sets arises from the low spatial autocorrelation of land surface properties [Townshend and Justice, 1988; Townshend and Justice, 1990]. Even in areas with near-natural land cover, spatial variability can exist at the finest scales due to local terrain variability and associated microclimatic influences on vegetation types and associations. Human-induced changes, such as deforestation, are the source of many of the finest-scale alterations and can significantly drive global change. Currently, we have very poor data on where land cover is being changed, what changes are occurring, and the land cover properties of the altered land [Townshend et al., 1991].