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• <br /> We have assessed the time commitment needed to complete the entire West Slope and have <br /> addressed the need for updating the data every 5 years. <br /> A. Assessment of USBR's ability to Meet State's spatial data needs. <br /> The USBR provided two sets of imagery, which are critical to this project, and saved the State of <br /> Colorado an estimated $54,000. The LandSat Thematic Mapper imagery, and the Digital <br /> Orthophoto Quarter Quadrangles. The Satellite Imagery enabled irrigated vs non-irrigated, and <br /> crop type analysis, while the DOQQ's enable the accurate delineation of field boundaries. <br /> The classification that the USBR provided does not meet the needs of our study, as shown in <br /> Exhibit A. Their classification using 30m data is not detailed enough to delineate our field <br /> boundaries with the necessary accuracy. <br /> For this project the USBR provided 4-meter DOQQ's. We "heads-up" (from the screen) digitized <br /> from the 4-meter data. Near the end of the project they received 1m DOQQ's, which we could use <br /> to perform the rest of the West Slope. These data are much more accurate, as illustrated in <br /> Exhibit I. <br /> B. Assessment of the State's 1993 Polygon coverage. <br /> The 1993 polygon map is a good representation of the conditions that existed in 1993, it can be <br /> used to help reduce data attributing, guide field delineation and to quantify temporal changes in <br /> irrigation. However its use as a base from which to build the new data set is not recommended. <br /> There is a fundamental registration problem associated with the 1993 data. The fields were <br /> digitized off of paper photographs, which were unable to be completely corrected for curvature <br /> effects. To match these polygons with the digital picture, 92.33% of the lines had to be shifted. In <br /> addition, the shifts were not uniform. The workload associated with shifting is more than starting <br /> from scratch. <br /> The 1993 polygon map can be used for the following: <br /> • To describe the irrinrtion status that existed in 1993. <br /> • To quantify temporal changes. For example, by comparing the total acreage from 1993 to <br /> 1999 we showed a 38% decrease in total area irrigated, a 48% change in crop type, and a <br /> 14% reduction in the number of polygons. • <br /> • To greatly reduce the workload of creating attribute data for each polygon. We used a <br /> method called "Identity" to transfer the attributes of the nearest (intersecting) polygon from <br /> the 1993 map to the 1999 map. One attribute was the Structure ID. After the Identity was <br /> performed, each polygon had an associated ID, and it was a process of QA/QC instead of <br /> data entry, and the data were correct 90% of the time in this study area. <br /> 3 <br />