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Common Land Unit (CLU) Dataset Projection: Geographic (Lat/Long), NAD83 Format: ESRI Shapefile Data Overview: The common land unit (CLU) dataset consists of digitized farm tract and field boundaries and associated attribute data. The USDA Farm Service Agency (FSA) defines farm fields as agricultural land that is delineated by natural and man-made boundaries such as road ways, tree lines, waterways, fence lines, etc. Field boundaries are visible features that can be identified and delineated on aerial photography and digital imagery. Farm tracts are defined by FSA as sets of contiguous fields under single ownership. Common land units are used to administer USDA farm commodity support and conservation programs in a GIS environment. The CLU data set was prepared by digitizing farm tracts and fields using 1:7920 scale rectified photomaps that have been maintained by FSA in USDA Field Service Centers. Using the photomaps as reference tract and field boundaries were digitized on-screen with digital orthophotography using ESRIs (Environmental Systems Research Institute) ArcView GIS Product. Each of the boundaries of the CLU are digitized to a tolerance of 3 meters (approximately 10 feet) from ground features visible on the digital orthophotograph. The base ortho imagery was produced by mosaicking digital orthophoto quarter quads (DOQs) into a seamless county image. The CLU were digitized from an image base of digital ortho quadrangles mosaiked together creating a seamless image base. The moasaicking process eliminates or minimizes any offset that would normally be present between standard USGS quarter quadrangles. |
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