i15 LandUse Tulare2007

This map is designated as Final.Land-Use Data Quality ControlEvery published digital survey is designated as either ‘Final’, or ‘Provisional’, depending upon its status in a peer review process. Final surveys are peer reviewed with extensive quality control methods to confirm that field attributes reflect the most detailed and specific land-use classification available, following the standard DWR Land Use Legendspecific to the survey year. Data sets are considered ‘final’ following the reconciliation of peer review comments and confirmation by the originating Regional Office. During final review, individual polygons are evaluated using a combination of aerial photointerpretation, satellite image multi-spectral data and time series analysis, comparison with other sources of land use data, and general knowledge of land use patterns at the local level.Provisionaldata sets have been reviewed for conformance with DWR’s published data record format, and for general agreement with other sources of land use trends. Comments based on peer review findings may not be reconciled, and no significant edits or changes are made to the original survey data.The 2007 Tulare County land use survey data was developed by the State of California, Department of Water Resources (DWR) through its Division of Integrated Regional Water Management (DIRWM) and Division of Statewide Integrated Water Management (DSIWM), Water Use Efficiency Branch (WUE). Digitized land use boundaries and associated attributes were gathered by staff from DWR’s South Central Region (SCRO), using extensive field visits and aerial photography. Land use polygons in agricultural areas were mapped in greater detail than areas of urban or native vegetation. Prior to the summer field survey by SCRO, WUE staff analyzed Landsat 5 imagery to identify fields likely to have winter crops. The combined land use data went through standard quality control procedures before final processing. Quality control procedures were performed jointly by staff at DWR’s WUE Land Use Unit and SCRO. This data was developed to aid DWR’s ongoing efforts to monitor land use for the main purpose of determining current and projected water uses. The associated data are considered DWR enterprise GIS data, which meet all appropriate requirements of the DWR Spatial Data Standards, specifically the DWR Spatial Data Standards version 2.1, dated March 9, 2016. DWR makes no warranties or guarantees - either expressed or implied - as to the completeness, accuracy, or correctness of the data. DWR neither accepts nor assumes liability arising from or for any incorrect, incomplete, or misleading subject data. Comments, problems, improvements, updates, or suggestions should be forwarded to gis@water.ca.gov. This data represents a land use survey of western Madera County conducted by DWR, South Central Regional Office staff, under the leadership of Steve Ewert, Senior Land and Water Use Supervisor. The field work for this survey was conducted during the summer of 2011. SCRO staff physically visited each delineated field, noting the crops grown at each location. Land use field boundaries were digitized using 2006 National Agriculture Imagery Program (NAIP) imagery as the base reference. Roads and waterways were delineated from a countywide shapefile using the U.S. Census Bureau's TIGER® (Topologically Integrated Geographic Encoding and Referencing) database and then clipped to match the USGS quadrangle boundaries. Digitized field boundaries were created on a quadrangle by quadrangle basis. Digitizing was completed at 1:4000 scale for the entire survey area. Field boundaries were delineated to depict observable areas of the same (homogeneous) land use type. Field boundaries do not represent legal parcel (ownership) boundaries, and are not meant to be used as formal parcel boundaries. Field work for DWR land use surveys typically occur during the summer and early fall agricultural seasons, so it can be difficult to identify fields where winter crops have been produced earlier during the survey year. To improve the mapping of winter crops, Landsat 5 imagery was analyzed to identify fields with high vegetative cover in late winter/early spring. Visual inspection of the Landsat scene displayed in false color infrared was used to select fields with both high and low vegetative cover as training data sets. These fields were used to develop spectral signatures using ERDAS Imagine and eCognition Developer software. The Landsat image was classified using a maximum likelihood supervised classification to label each pixel as vegetated or not vegetated. Then, the zonal attributes of polygons representing agricultural fields were summarized to identify fields vegetated during the winter. Polygons representing potential winter crops were used as an additional reference during field visits, and closely checked for winter crop residue. Site visits occurred from July through October 2007. Images and land use boundaries were loaded onto laptop computers that, in most cases, were used as the field data collection tools. GPS units connected to the laptops were used to confirm the surveyor's location with respect to each field. Some staff took printed copies of aerial photos into the field and wrote directly onto these photo field sheets. The data from the photo field sheets were digitized and entered back in the office. Land use codes associated with each polygon were entered in the field on laptop computers using ESRI ArcGIS software, version 9.3. Virtually all delineated fields were visited to positively observe and identify the land use type. 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. Rural residential land use was delineated by drawing polygons to surround houses and other buildings along with some of the surrounding land. These footprint areas do not represent the entire footprint of urban land. Sources of irrigation water were identified for general areas and occasionally supplemented by information obtained from landowners. Water source information was not collected for each field in the survey, so the water source listed for a specific agricultural field may not be accurate. Before final processing, standard quality control procedures were performed jointly by staff at DWR's South Central Region, and at DSIWM 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 orthorectified NAIP imagery, is approximately 6 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.