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MEMO -TASK 90.2 <br />Figure 1. Irrigated Field Mapping <br />Print Multi date NDVI <br />Combined Image Base Map and NDVI composite for <br />Combined Image Base Map and DRG identifying <br />NDVI composite irrigated lands <br />Interpret maps <br />and draw Image base map <br />field boundaries and Digital <br />Raster Graphics <br />Check field boundaries <br />for consistency with <br />procedures and <br />guidelines <br />Digitize field <br />boundaries from <br />drawn maps <br />QAQC field boundaries Irrigated Parcel <br />for consistency and Maps <br />positional accuracy (Bra) <br />1. Printing Maps. Large format maps were printed for the portions of the study area with <br />potentially irrigated land. These maps aided in interpreting and drawing the irrigated field <br />boundaries. The maps were in a convenient size and a scale of 1:16,000, 1:24,000, or 1:40,000, <br />depending on the complexity of the area. Three maps were printed for each area, described as <br />follows: <br />a. The first map had only the DOQQ overlaid with contour lines derived from the USGS Digital <br />Raster Graphics (DRG) topographic quadrangle data at 1:24,000 scale. An example of the <br />DOQQ with DRG overlay is shown in Figure 2a. These maps were used for primary photo <br />interpretation of irrigation status. The contour lines were useful for interpreting the slope of <br />potentially irrigated land and its landscape position relative to ditch alignment or other <br />features. <br />b. The second map had the DOQQ overlaid with the semi-transparent NDVI composite <br />classification product, described in the memo for Subtask 89.1. An example is shown in <br />Figure 2b. Irrigated lands and changes in field boundaries between the date of DOQQ aerial <br />photography and 2001 satellite imagery were identified on this map. These maps were used <br />as the base for drawing irrigated field boundary lines. Changes in field boundaries, detected <br />by the 30 m Landsat imagery, were mainly due to differences in crop type within a larger, <br />contiguously irrigated area. An example can be seen in Figure 2a and 2b. In the middle of <br />the right side of each image is a center pivot that shows as mostly irrigated in the NDVI <br />composite (Figure 2b). The two colors, yellow and purple, indicate that this center pivot is <br />Page 2 of 6 ~Rlverslde Technology, lnc. <br />Gr:HS•: Rx:soarcc~s En;:ncer~nc.~~ad cuns.nrmc <br />