The United States Department of Agriculture (USDA), National
Agricultural Statistics Service (NASS) area sampling frame is a
delineation of all parcels of land for the purpose of later sampling the
parcels. The area frame is constructed by visually interpreting satellite
imagery to divide a state into homogenous land use areas (strata) based
on percent cultivated. The strata are typically defined as low, medium or
high percent cultivated, non-agricultural land, urban use, agri-urban, or
water. The boundaries of the strata usually follow identifiable features
such as roads, railroads and waterways. The strata boundaries do not
coincide with any political boundaries, with the exception of state
boundaries.
Though all of the date for this frame point to 2014, this is only when a set
of additional strata was added to the frame. For the survey year of 2014 the
Cropland Data Layer was used to add a layer that is durum wheat. Before this,
the entire state was stratified to Landsat satellite imaging and completed for
the survey year 2011.