The Great River Environmental Action Team (GREAT) was a federal/state multi-agency cooperative program established in the late 1970's to evaluate current resource management practices and develop management strategies for the Upper Mississippi River (UMR). One of the problems facing the GREAT project was the lack of available information on many of the river's components. One project implemented by GREAT was the creation of a land cover/land use (LCU) database derived from color infrared aerial photography collected in 1975. Mississippi River Pools 3 through 10 were photographed at a scale of 1:9,600, and Lock and Dam 10 to the Ohio River were photographed at a scale of 1:24,000. The program's photo interpreters delineated whatever features could be viewed on the photos, using a minimum mapping unit that was less than half an acre. A contractor was hired to transfer the photo overlays for Pools 3 through 14 onto 1:24,000-scale USGS quadrangles, then automate the data using the geographic information system (GIS) program PIOS. The data were also distributed as map books that contained 1:6,000-scale enlargements of the photos and their overlays. During the data transfer process; the contractor hired to automate the data generalized it to a 2.5 acre minimum mapping unit. Documentation archived by the GREAT project described this automation process as; some polygons smaller than 2.5 acres and linear features were incorporated into nearby polygons. Others were manually enlarged so that the data contained within would be preserved. All generalizations were made in accordance with the guidelines established for the GREAT projects. The digital data sets were then enhanced by the GREAT project. Unfortunately no record of the enhancements or an archive of the original digital dataset are known to exist. The enhanced digital data, copies of the aerial photo overlays, copies of most of the map books, and some of the photos themselves were archived and preserved by the various agencies that participated in the GREAT project. These data were then passed to the Upper Midwest Environmental Sciences Center (UMESC) in the late 1980's and 1990's when the center became the administrator for the Upper Mississippi River System's Long Term Resource Monitoring Program(LTRMP). Comparisons of the archived digital data set to the photos and their overlays displayed discrepancies that were difficult to document. The 1975 data set is viewed by many as an important baseline data set, so in 1999 UMESC decided to use the archived photo overlays to (1) address the data discrepancies by reautomating Pools 3 through 14, and (2) complete the data set by automating Lock and Dam 14 to the Ohio River.

Full metadata available at:

http://umesc.usgs.gov/data_library/umesc_metadata/land_cover/umesc_1975_lcu.html