Sanborn Map Company, Inc. 20200512 raster digital data Product: Hydro-flattened bare-earth digital elevation model data. Geographic Extent: Brazos County, TX, covering the approximately 155 square miles. Dataset Description:The College_Station_TX_Lidar project called for the planning, acquisition, processing and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.35 meters (QL1). Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 1.3. The data was developed based on a horizontal projection/datum of NAD83 (2011), State Plane, U.S. Survey Feet and vertical datum of NAVD88 (GEOID12B), Feet. Lidar data was delivered as processed Classified LASv1.4 files, formatted to 794 individual 2,500 ft x 2,500 ft tiles clipped to the BPA, and as 794 individual 2,500 ft x 2,500 ft tiled intensity imagery, tiled bare-earth DEMs, and contours. Ground Conditions: Lidar was collected in early 2020, while no snow was on the ground and rivers were at or below normal levels. In order to post process the lidar data to meet task order specifications and meet ASPRS vertical accuracy guidelines, The Sanborn Map Company, Inc. established a total of 7 ground control points that were used to calibrate the lidar to known ground locations established throughout the project area. An additional 25 independent accuracy check points, 20 in Open Terrain/Bare-Earth and Urban landcovers (20 NVA points), 5 in Grass, Brush and Trees categories (5 VVA points), were used to assess the vertical accuracy of the data. These check points were not used to calibrate or post process the data. To acquire detailed surface elevation data for use in conservation planning, design, research, floodplain mapping, dam safety assessments and elevation modeling, etc. Classified LAS files are used to show the manually reviewed bare-earth surface. This allows the user to create Intensity Images, Breaklines and Raster DEM. The purpose of these lidar data was to produce high accuracy 3D hydro-flattened Digital Elevation Model (DEM) with a 1 foot cell size. These raw lidar point cloud data were used to create classified lidar LAS files, intensity images, 3D breaklines, hydro-flattened DEMs, and contours necessary. 1 foot, 32-bit digital elevation models in GeoTIFF format interpolated from a triangulated irregular network that meets a 19.6 cm NVA requirement. 20200225 20200227 ground condition Complete None planned -96.4234904459 -96.1359033831 30.6584128237 30.4440751502 None Model Raster DEM Remote Sensing Elevation Data Lidar None Texas Brazos No restrictions apply to these data. None. However, users should be aware that temporal changes may have occurred since this dataset was collected and that some parts of these data may no longer represent actual surface conditions. Users should not use these data for critical applications without a full awareness of its limitations. Acknowledgement of the U.S. Geological Survey would be appreciated for products derived from these data. Data covers the entire area specified for this project. Datasets contain complete coverage of tiles. No points have been removed or excluded. A visual qualitative assessment was performed to ensure data completeness. There are no void areas or missing data. The raw point cloud is of good quality and data passes Non-Vegetated Vertical Accuracy specifications. The project specifications require the accuracy (ACCz) of the derived DEM be calculated and reported in two ways: 1. The required NVA is: 19.6 cm at a 95% confidence level, derived according to NSSDA, i.e., based on RMSE of 10 cm in the "bare earth" and "urban" land cover classes. This is a required accuracy. The NVA was tested with 20 check points located in bare earth and urban (non-vegetated) areas. 2. Vegetated Vertical Accuracy (VVA): VVA shall be reported for "brushlands/low trees" and "tall weeds/crops" land cover classes. The target VVA is: 30.0 cm at the 95th percentile, derived according to ASPRS Guidelines, Vertical Accuracy Reporting for Lidar Data, i.e., based on the 95th percentile error in all vegetated land cover classes combined. This is a target accuracy. The VVA was tested with 5 check points located in tall weeds/crops and brushlands/low trees (vegetated) areas. The check points were distributed throughout the project area and were surveyed using GPS techniques. See survey report for additional survey methodologies. AccuracyZ has been tested to meet 19.6 cm or better Non-Vegetated Vertical Accuracy at 95% confidence level using RMSE(z) x 1.9600 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASRPS Guidelines. 0.249 Tested 0.249 feet NVA at a 95% confidence level using RMSE(z) x 1.9600 as defined by the National Standards for Spatial Data Accuracy (NSSDA). The NVA of the DEM was calculated using 20 independent check points located in the Bare Earth and Urban land cover categories. 0.299 Tested 0.299 feet VVA at the 95th percentile was calculated using 5 check points located in the Brushlands and Low Trees and Tall Weeds and Crops land cover categories, derived according to ASPRS Guidelines, Vertical Accuracy Reporting for Lidar Data. Tested against the DEM. Hydro-Flattened Raster DEM Process: Class 2 (ground) lidar points in conjunction with the hydro breaklines were used to create a 1 foot hydro-flattened Raster DEM. Using automated scripting routines within LP360, a TIFF file was created for each tile. Each surface is reviewed using Global Mapper to check for any surface anomalies or incorrect elevations found within the surface. 20200727 Raster Pixel 2500 2500 NAD 1983 2011 StatePlane Texas Central FIPS 4203 Ft US 31.88333333333333 30.11666666666667 -100.3333333333333 29.66666666666667 2296583.333 9842500.000000002 coordinate pair 0.001 0.001 foot D NAD 1983 2011 GRS 1980 6378137.0 298.257222101 North American Vertical Datum of 1988 0.001 foot Explicit elevation coordinate included with horizontal coordinates 20200727 The Sanborn Map Company, Inc. mailing and physical

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