This dataset is derived from a combination of satellite imagery and national level census data using an algorithm developed by Navin Ramankutty of the University of Wisconsin-Madison. Although this image is for 1992, the dataset was originally compiled as part of a historical croplands dataset that runs from 1700 to 1990.
The grid contains fractional crop-cover data, meaning the number given for each gridcell is the fraction of that gridcell’s surface that is covered by crops. Thus a value of 0.7 means that 70 percent of the cell is being used for agricultural purposes.
Ramankutty, N., and J.A. Foley (1999). Estimating historical changes in land cover: North American croplands from 1850 to 1992. Global Ecology and Biogeography 8, 381-396.
(All images are provided at a resolution of 1600×1200 pixels)
Download a GIS grid of this data (ESRI ArcView Format)
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