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<br />. <br /> <br />~ <br />I <br />~) <br />W <br />~ <br />...:.t <br /> <br />. <br /> <br />. <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 />smaller sub-fields on the basis of irrigation ditches, fences, or <br />differences in cropping pattern. If two portions of a larger field are <br />cropped differently, the field should be subdivided. The most <br />current photo date is used for determining the field outlines. <br />4) Freshly plowed ground often appears 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 />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 tracking sprinkler systems. <br />3) Potentially irrigable 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 />during the spring and fall than in summer. <br /> <br />State Engineer's Review <br /> <br />Mter the photo interpretation, the mylars 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 />