2009 Cropland Data Layer
By Nancy Rader, MnGeo
The U.S. Department of Agriculture’s Cropland Data Layer Program uses satellite imagery on an annual basis to produce a land cover data layer showing specific crops and to provide supplemental acreage estimates for the state's major commodities. CDL data is available for Minnesota for 2006-2009.
CDL is a geo-referenced, categorized land cover data layer produced using satellite imagery from Landsat Thematic Mapper (TM) or RESOURCESAT Advanced Wide Field Sensor (AWiFS). The approximate scale is 1:100,000 with a ground resolution of 30 meters by 30 meters for the TM data, 56 meters by 56 meters for the AWiFS data. CDL is provided in GeoTIFF raster format.
The data is aggregated to a possible 85 standardized categories for display purposes, with the emphasis being agricultural land cover. Most data layers average about 10 to 20 categories out of the 85 possible categories. Agricultural training and validation data are derived from the Farm Service Agency (FSA) Common Land Unit (CLU) Program.
The CDL Program annually focuses on the corn/soybean/rice/cotton agricultural regions in the Midwestern and Mississippi Delta States. It is a cooperative venture between three USDA agencies (the National Agricultural Statistics Service, the Foreign Agriculture Service IPA group and the FSA/Aerial Photography Field Office) plus in-state agreements between NASS field offices and their respective state government or university partners. No farmer-reported data are derivable from CDL.
Obtaining the Data
The data may be downloaded at no charge from these websites:
• USDA-NASS website: Also see the order form for all years on DVD at the cost of reproduction.
• NRCS Geospatial Data Gateway: includes some earlier years for other states (see status map).
Using the Data
Minnesota’s state Department of Agriculture (MDA) has been using the CDL for a few years now, with mixed success but overall satisfaction. “Before the CDL, we had very few options for geospatial information on crops that was accurate, accessible, and comprehensive. Now, every year we get an authoritative data source that meets most of our needs, and we’re very happy about that,” says Mike Dolbow, MDA’s GIS Coordinator.
MDA’s only caution about the data is potential performance problems when working with the entire state. In order to perform simple acreage calculations or other statistical analysis, MDA’s Karl Hillstrom has had to clip the information down to the size of individual counties. Nevertheless, it has proved valuable for various individual applications, such as Potato Cyst Nematode surveys or monitoring watersheds for certain pesticides that are frequently applied to specific crops.
Hillstrom notes that “overall, the CDL provides a great look at agricultural distributions across Minnesota, and is particularly valuable for seeing crop distributions when you only display one or two crops at a time, like corn, soybeans, or sugar beets, which have very distinctive ranges.”
See the USDA-NASS website for an FAQ section and metadata as well as contact information for further questions.