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MEMO 89.2 <br />to find on a strictly random basis, such as `Dry Beans' and `Vegetables'. These lists were used to <br />obtain an adequate amount of information for these crop types. <br />d) Information extraction. Using the lists of verified and difficult to find crops described above, <br />RTi obtained the corresponding farmer records from FBA's file cabinets. Subsequently, all 2001 <br />mapsZ in each of the farmer records were photocopied. An example of one of these maps is shown in <br />Figure 6. In addition to crop type, information on irrigation status (i.e., irrigated or non-irrigated) <br />was obtained from the records. <br />Figure 6. Example of Reference Information Obtained from an FSA Map <br />e) Reference shapefile development. The reference data obtained from FSA in the form of <br />photocopies, as described above, was digitized in ArcGIS using DOQQ3, NDVI Imagery4, and Public <br />Land Survey System data. A buffer distance was excluded when delineating polygons for extraction <br />of reference data, as recommended in a recent South Platte River basin study (Cipra, 2003) in order to <br />avoid mixed-pixels on the edge of parcels (Figure ~. <br />~ Producers update parcel boundaries and crop type information annually on photocopies of aerial photos acquired by the National Aerial <br />Photography Program (NAPP) in the late 1980s and earlier. Most maps contain Public Land Survey System (PCBs) Township-Range-Section <br />information that facilitates their location, although this varies within FSA offices. Alternatively, parcels can be located on photographs by farm, <br />track number, and parcel LD., which in turn can be related to an aerial photo index map. <br />s DOQQs provide detail spatial information. <br />' NDVI Imagery provided temporal and spectral information <br />Page 11 of 45 ~Rlversfde FecAnotogy, fnc. <br />4'JaYer Resources Errgi~ecr:np an~i CansuFlrnp <br />