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Table 1. Comparison of Satellite and Aerial Capabilities used in SPDSS Mapping <br /> <br />Sensor Spatial Resolution/ Number of Radiometric <br /> Scale Bands Resolution) <br />Landsat ETM+ (Landsat 7 -Enhanced 30 meter multispectral 8 bands 8 bit <br />Thematic Mapper Plus) <br />Landsat TM (Landsat 5 -Thematic 30 meter multispectral 7 bands 8 bit <br />Mapper) <br />Landsat MSS (Landsat 1,2,3 - g0 meter multispectral 4 bands 6 bit <br />Multispectral Scanner) <br />1950s Aerial Photos 1:24,000 Panchromatic only N/A <br />1950s Aerial Photo Indexes Varies - 1:63,360 panchromatic only N/A <br /> (Approximately) <br />1 Radiometric Resolution (bit depth) is the sensitivity of the sensor's detectors to differences in detail. 8-bit data corresponds to image values of <br />0-255, while a 4-bit data corresponds to image values of 0-63. <br />Landsat TM data have been available only since 1982; therefore, Landsat MSS data were assessed for the <br />1970s irrigated lands analysis. Some Landsat MSS scenes were acquired that contain areas of poor <br />radiometric quality (striping and/or banding) and/or cloud cover in irrigated areas. These scenes were <br />purchased regardless of these factors because non-affected areas within the scene were needed to provide <br />more coverage of the SPDSS area. Poor quality images were rejected. <br />Table 2 and Table 3 summarize acquired Landsat imagery identified using the described criteria. These <br />summary tables include a total of 48 images with 20 scenes for 1987 and 28 scenes for 1976. For 1987, <br />five image frames cover the study area with an average of 5 dates acquired per frame. For 1976, six <br />image frames cover the study area with an average of 6 dates acquired for each frame. As described in <br />SPDSS Draft Memorandum for Task 89.1, multi-date satellite imagery significantly improves irrigated <br />lands and crop discrimination. The cost associated with Landsat images varied per sensor system and <br />available USGS discounts were utilized. Single scene Landsat TM was $425, while single scene Landsat <br />MSS cost was $200. The total cost for purchased imagery was $13,420. <br />3. Aerial Photography Purchase <br />This section summarizes aerial photography acquired for mapping historic irrigation in the SPDSS in the <br />1950s. The Farm Service Agency (FSA) and USGS acquired the majority of all 1950s aerial photography <br />collected. This historic aerial photography is commercially available through the FSA operated Aerial <br />Photography Field Office (APFO) in Salt Lake City, UT. The APFO publishes a list of available photos <br />and photo indexes for historically acquired data organized by state counties. The photo index is a reduced <br />resolution "collage" of acquired imagery in each county. The photo index is an actual picture of the <br />individual aerial photo prints arranged and stapled together. Figure 1 shows a subset of a 1957 photo <br />index in Larimer County between Lake Loveland and Boyd Lake along Highway 34 in Loveland. Aerial <br />photography indexes through the APFO cost $20 each. Table 4 summarizes the acquired photo indexes <br />per county within the SPDSS study area and total cost. Neither photos nor indexes were available from <br />the APFO for Park, Clear Creek, and Teller counties in the 1950s. However, RTi was provided a small <br />quantity of Park county historic aerial photos from an independent consultant. This imagery was acquired <br />for the City of Aurora for analysis of water resources. While the majority of the Park County photos are <br />site specific and for various years in the 1930s through the 1980s, it is anticipated that the City of Aurora <br />aerial photos will be useful for mapping 1950s irrigation practices in Park County. <br />Page 2 of 6 ~1~~vers#de Technology, Inc. <br />l"Aalc: Resources Engrnee.•rag antl L'nnsufVing <br />