i15 LandUse Trinity2006

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 2006 Trinity 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). Land use boundaries were digitized and land use data was gathered by staff of DWR’s Northern Region using extensive field visits and aerial photography. The land uses that were mapped were detailed agricultural land uses, and lesser detailed urban and native vegetation land uses. The land use data went through standard quality control procedures before final processing. Quality control procedures were performed jointly by staff at DWR’s DSIWM headquarters and Northern Region, under the supervision of Tito Cervantes, Senior Land and Water Use Scientist. 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 Trinity County conducted by the California Department of Water Resources, Northern Region Office staff. Data development: Trinity County was surveyed using the 2005 one-meter resolution National Agriculture Imagery Program (NAIP) digital aerial photos from the U.S. Department of Agriculture's Farm Services Agency as a base for line work. Digital 7.5’ quadrangle sized images were created from the 2005 NAIP imagery. In the spring of 2006, DWR's Northern Region staff digitized land use boundaries using AutoCAD Map software. The digital images and land use boundaries were copied onto laptop computers that were used as the field data collection tools. Staff visited all accessible fields to positively identify agricultural land uses. These site visits occurred between June and August 2006. Land use codes were digitized directly into the laptop computers in the field using AutoCAD Map (using a standardized digitizing process). Some staff took 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 using AutoCAD Map back in the office. For both data gathering techniques, any land use boundary changes were noted and then corrected in the office. The primary focus of this land use survey is mapping agricultural fields. Urban residences and other urban areas were delineated using primarily aerial photo interpretation, so some urban areas may have been missed. In some rural residential areas, urban land use was delineated by drawing polygons to surround houses or other buildings along with a minimal area of land surrounding these structures. These footprint areas represent the locations of structures but do not represent the entire footprint of urban land. Sources of irrigation water were not mapped in this survey. The linework and attributes from each AutoCAD drawing file were brought into ArcInfo and both quadrangle and survey-wide coverages were created, and underwent quality checks. The coverages were converted to shapefiles using ArcView. After quality control procedures were completed on each file, the data was finalized. 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 orthorectified NAIP imagery, is approximately 6 meters, but in some areas linework may be 10 meters from the actual location. 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.