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<br />OJJJ43 <br /> <br />determining field locations. Spectrally, the extensive riparian areas and the <br />irrigated upland pastures are difficult to distinguish. For this reason, <br />satellite images are not particularly effective for differentiating between <br />irrigated and dry-land agriculture in the UC. To alleviate"this problem, an <br />ARC/INFO database of field boundaries is being developed. The vector <br />database will provide more accurate acreage figures. The satellite imagery <br />is being used to infill where crop type.information is not known. <br />. . <br /> <br />The western slope of Colorado has been divided into ten subareas <br />based upon major watershed locations. These subareas are only . <br />approximations however, because they are composed of 1:24,000 scale <br />USGS quads. Field boundary vector data are being developed by subarea. <br />The six major steps required are: . <br /> <br />. . <br /> <br />1) Interpret theCIR (color infrared) photos .and transfer to mylar <br />()verray onanorthophoto base map <br />. 2) scan or matJ;u;ally digitize the mylar overlay <br />3) Edit the scan.rtedfile in ARC/INFO <br />4) Produce a draft plot which overlays a USGS 1:24,000 map <br />5) Send the plots to the Colorado State Engineer for review <br />6) Update the ARC/INFO file from the State Engineer's review and <br />add crop type information where applicable <br />. . <br /> <br />Photo Interpretation <br /> <br />There are 445 1:24,000 USGS quads in Colorado that are contained <br />within the Upper Colorado River Basin. Extensive technical assistance (0- <br />3744 staff) has been necessary to manage the large numbers of quads and <br />corresponding aerial photographs required to develop the ARC/INFO <br />database. The following materials and methods have been used to <br />standardize the aerial photo interpretation: <br /> <br />. Tools <br /> <br /> <br />Drafting Pens - 00 (0.012") for clean lines (at 1:24,000 a 0.012" line = <br />24 feet) <br /> <br />,}I~lr~llilliti~;s~~~~ut <br /> <br />distortion . . <br />1:25,000 NHAPP or 9" CIR photos - provide current land use <br />7.5 Minute Quads - show topography, streams, ditches, etc~ <br />Light Table- for back lighting the orthophotos <br /> <br /> <br />2 <br />