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This data represents a land use survey of Butte County conducted by DWR, Northern District Office staff, under the leadership of Tito Cervantes, Senior Land and Water Use Supervisor. The field work for this survey was conducted during the summer of 2004. ND staff physically visited each delineated field, noting the crops grown at each location. Field survey boundary data was developed using: 1. The county was surveyed using the 2005 one-meter resolution National Agriculture Imagery Program (NAIP) digital aerial photos as a digital reference for line work and field work. 2. From the 2005 NAIP imagery, digital 7.5’quadrangle sized images were created, with one-meter resolution. These were used in the spring of 2006 to develop the digital land use boundaries that would be used in the survey. The digitizing of these boundaries was done using AutoCAD Map software. 3. The digital images and land use boundaries were copied onto laptop computers that, in most cases, were used as the field data collection tools. The staff took these laptops into the field and virtually all the areas were visited to positively identify the agricultural land use. The site visits occurred between June and August 2006. Land use codes were digitized directly into the laptop computers using AUTOCAD (using a standardized digitizing process). Some staff took the printed aerial photos into the field and wrote land use codes directly onto these photo field sheets. The data from the photo field sheets were digitized back in the office. For both data gathering techniques any land use boundary changes were noted and corrected in the office. Urban and native classes of land use were mapped by both field observation and photo interpretation.4. The linework and attributes from each quadrangle drawing file were brought into ARCINFO and both quadrangle and survey-wide coverages were created, and underwent quality checks. These coverages were converted to shapefiles using ArcMAP. 5. After quality control/assurance procedures were completed on each file, the data was finalized. The primary focus of this land use survey is mapping agricultural fields. Urban residences and other urban areas were delineated using aerial photo interpretation. Some urban areas may have been missed, especially in forested areas. Before final processing, standard quality control procedures were performed jointly by staff at DWR's Northern District, and at DPLA headquarters under the leadership of Jean Woods, Senior Land and Water Use Supervisor. After quality control procedures were completed, the data was finalized. The positional accuracy of the digital line work, which is based upon the 2005 one-meter resolution National Agriculture Imagery Program (NAIP), is approximately 12.1 meters. The land use attribute accuracy for agricultural fields is high, because almost every delineated field was visited by a surveyor. The accuracy is 95 percent because some errors may have occurred. Possible sources of attribute errors are: a) Human error in the identification of crop types, b) Data entry errors. |