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<br />oan05'] <br /> <br />of center pivot irrigation systems,etc). <br /> <br />Aerial Photo Interpretation <br /> <br />1) The 9-inch CIR and 1:25,000 NHAPP photos used for this project are <br />distorted. The distortion is most noticeable near the edges and in <br />the corners of the photos. When overlapping images are available, <br />use only the center portion of each for interpretation to minimize <br />distortions. . <br />'2) Most of the irrIgated fields are easy to distinguish on CIR photos <br />taken during the summer months. The dense vegetation found on <br />well-irrigated land shows up in shades of red. <br />3) Many of the field boundaries are visible on the orthophoto. quad and <br />can be traced onto the mylar. Most large fields can be broken into <br />srnallersub-fieltlsonthe basis of irrigation ditches, fences, or <br />diff~r~~ceSlncro,ping.pattem. If two portions of a larger field.are <br />cr()PJred.differ~l'ltly,~e,;fieldshouldbe. subdivided. . The Ifiost <br />current photo date is used for determining-the field outlines. <br />-4) Freshly plowed ground often app_ears in shades of blue, green, pink, <br />and/or gray-green on CIR photography. The individual furrows may <br />be visible as well as irrigation ditches or fences delineating the field. <br />5) Texture is as important to the interpretation as the color. Cropped <br />areas normally appear smooth when compared to areas covered by <br />scrub brush or riparian vegetation. <br /> <br />Caveats <br /> <br /> <br />1) If in doubt, delineate the field. It is better to have too many field <br />boundaries than too few. <br />2) Not all irrigated fields Will contain irrigation ditches. Other forms of <br />irrigation include: center pivot systems, surface flood piping, and <br />linear traeldng sprinkler systems. <br />3) Potentlallylrrigable-is a nebulous term. If there appears to be <br />evidence that the field has been, or is currently receiving water, it <br />should be delineated. <br />4) The photo date should be noted. Irrigation effects are less prominent <br />~d9:~~p.~'ith~spril1~>~c;l JaJlth~ In. SUll'lm~r. .. <br /> <br /> <br />.' ., " .." <br />.'-0.... ,,' ,- - '.~ . <C..... :'. ..:. ,....,. . ." ,', - _.. <br />sta,t~..~~gtI1e~r"s':R~yie~'- <br /> <br />. '- . - - -.'- - .. .' . - - - - '-' -. . .- - .' ~ <br />" - -,'-,,:,.',:.:,""';"..'. ,. ---,. . . <br />- . . . . . <br /> <br />After the photo interpretation, the tnylars are scanned and converted <br />into ARC/INFO format. The files are then plotted on mylar, at 1:24,000 <br />scale, and sent to the State Engineer's office for review. Personnel in the . <br />division offices of the State Engineer have knowledge of the irrigation <br /> <br />4 <br />