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<br /> <br />. <br /> <br />o <br /> <br />'"."7) <br /> <br />w <br />ee <br />~ <br /> <br />. <br /> <br />. <br /> <br />INTRODUCTION <br /> <br />The primary objective of this study is to construct a regional GIS <br />(geographic information system) database, at 1:24,000 scale, delineating all <br />irrigated fields and open water surfaces within the Upper Colorado River <br />Basin. The acreage figures and crop type information can then be used to <br />derive more accurate consumptive water use estimates. In developing the <br />methodology for this project, efforts were made to gather and incorporate <br />previous work, such as existing maps and aerial photography. Cooperative <br />ventures have been established to effectively utilize state-level initiatives <br />and knowledge of field personnel. Satellite image processing techniques <br />are being employed to provide field inventory information for areas where <br />ancillary data are limited. . <br /> <br />The development of this regional GIS database involves three primary <br />phases: 1) vector database development, 2) satellite image processing, and <br />3) integration of the vector and raster data to produce acreages and crop <br />type information. These three phases will be discussed in this report. <br /> <br />VECTOR DATABASE DEVELOPMENT <br /> <br />Reclamation has been implementing GIS and Remote Sensing <br />technologies to facilitate development of the Consumptive Uses and Losses <br />Report. Due to land use differences between the Upper and Lower Colorado <br />River Basins, these technologies have been applied differently in the two <br />regions. <br /> <br />Analysis of Landsat TM (Thematic Mapper) imagery from the (LC) <br />Lower Colorado River Region states is relatively straightforward. To <br />differentiate irrigated crop land from the surrounding desert is not a <br />difficult task. For this reason, the LC office began using remote sensing <br />technology with only minimal use of GIS. The resolution of the TM imagery <br />(25 meter pixels) coupled with the rounding errors inherent in a raster <br />environment, produced inaccurate acreage estimates. In order to overcome <br />this problem, LC has used SPOT panchromatic imagery (10 meter pixels) to <br />delineate the field boundaries. The field boundaries are being digitized <br />directly on-screen using the SPOT imagery as a base. The primary difficulty <br />in the LC is not determining field locations, but crop type. Due to the long <br />growing season, multiple crops are produced. Agricultural practices in the <br />region require multi-date imagery to accurately determine crop types <br />throughout an entire year. <br /> <br />In the (UC) Upper Colorado River Region, the primary problem is <br /> <br />1 <br />