Title: Common Land Unit
Originator: USDA Farm Service Agency
A Common Land Unit (CLU) is the smallest unit of land that has a permanent, contiguous boundary, a common land cover and land management, a common owner and a common producer association.
A CLU is delineated from permanent features such as fence lines, roads, and or waterways. This requirement minimizes the number of changes that will be required in the CLU boundary.
Currently, all Service Center Agencies maintain a wide array of information related to land units. This information is fragmented among paper documents and computer systems. All this scattered information related to CLU's can be consolidated. The primary purpose of the CLU in electronic format is to provide the Field Service Center with an accurate method of reporting accurate acreages calculations and boundary information regarding the tracts and fields.
CLU's are currently being digitized to produce a CLU data layer. Digitizing involves using GIS to draw border lines on top of photography, calculate the area of the polygon and attach elements of data, such as a label or a field number or a record identifier, to this polygon shape. For Service Centers, these polygons will represent CLU boundary lines.
When the Common Land Unit tract and field boundaries are digitized from photography, a confidence level of 90% with a tolerance of three meters (approximately 10 feet) from ground features visible on the photography is used. The photomaps are an image base of digital ortho quadrangles mosaicked together creating a seamless image base which eliminates any offset that would normally be present between standard USGS quarter-quadrangles.
After digitizing, the CLU is topologically built, and a geographic projection is set. During topologic construction, all sliver polygons are dissolved. In counties that are split by multiple zones, the CLU is digitized to the image base mosaic which is projected to the predominate zone.
Each CLU defined in the GIS database will be automatically identified and tracked, for national purposes, with an ID number assigned by the automated system.
This ID is not visible to the user, but can be accessed when needed. The ID is a unique computer-generated number (GUID) that is created and will never be reused.
Format: vector polygon - Arc shapefiles
Spatial Reference Information: Universal Transverse Mercator (UTM) Dominant Zone, North American Datum 1983