Satellite imagery and geographic information systems are keeping agriculture, land use decisions and water quality issues on the map.

The National Agricultural Statistics Service is using GIS to develop cropland data layer maps. The maps outline individual fields of corn, soybeans and small grains, in addition to urban and forested areas, pasture land and bodies of water. These maps are now being made available to the public on CD-ROM.

The purpose of using GIS is to determine a more accurate acreage number in individual counties, said Ralph Gann, state statistician for the Indiana Agricultural Statistics Service, located at Purdue University.

"One of our missions is to establish county level production data each year," Gann said. "We get very good yield data from farm surveys on high, average and low yields. But, sometimes trying to determine how many acres were planted of each crop can be more difficult from a statistical point of view. This type of imagery really helps us narrow those margins down."

States that have this cropland data are Illinois, Indiana, Iowa, Nebraska, Missouri, Mississippi, Arkansas and North Dakota.

The greater value of this data may come in the future for smaller acreage crops like fruit, vegetables or other specialty crops where sample survey data can be more questionable, Gann said.

Groups studying issues such as land use, water quality, zoning, planning and deforestation rates also can use the cropland data layers. The U.S. Department of Agriculture, Farm Service Agency, National Resources Conservation Service and National Forest Service are looking at how this data can help them administer programs more effectively around the state, Gann said.

"Land use is a politically hot topic in many areas around the state," Gann said. "Of course, urban sprawl is one of those words many people encounter and the disappearance of farmland concerns them. This data can track over the years how land has been used. I think it will take some of the political volatility out of the discussions when so many people have a particular issue they want to promote without hard data."

The 2000 and 2001 cropland data maps on CD-ROM cost $35. No GIS software is needed to view the maps. Users can look at the entire state or select a specific area in a county. More information and an order form for the CD-ROM are on the NASS Web site at http://www.nass.usda.gov/research/Cropland/SARS1a.htm .

"When you put the data together over a period of time, it begins to tell a story," Gann said. "It builds a mosaic, and that is a term used to describe the features of what the land use looks like at any given point of time."

The U.S. Department of Agriculture has worked with GIS for more than 30 years. The technology was used during the 1970's to map foreign country's crop acreages, to determine potential demand for the U.S. crop.

In the late 1980's and 1990's, GIS mapping was used to assess U.S. crop stress caused by weather.