2017 NRCS Lidar DEM: East Sacramento Foothills, CA

Original Dataset Product: : 1-meter bare-earth raster digital elevation model (DEM) data tiles in ERDAS IMG format.

Original Dataset Geographic Extent: Approximately 1,399 square miles across several counties in central California. The counties are: Amador, Calaveras, Madera, Merced, Sacramento, San Joaquin, Stanislaus

Original Dataset Description: The CA Central Valley Lidar 2016 D16 lidar project called for the planning, acquisition, processing, and production of derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.7 meters. Project specifications were based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 1.2. The data was developed based on a horizontal datum/projection of NAD83 (2011) UTM Zone 10 (EPSG 6339) meters, and a vertical datum of NAVD88 (GEOID12B), US Survey Feet. DEM data was delivered as ERDAS IMG files formatted to 1,931 individual 1,500-meter x 1,500-meter tiles.

Original Dataset Ground Conditions: Lidar was collected from December 3, 2017 through December 7, 2017 by Woolpert, while no snow was on the ground and rivers were at or below normal levels. Saturated or partially flooded farm fields were identified following data acquisition. Through technical guidance discussions with USGS and the California Department of Water, it was determined such areas shall not be considered hydrologic features. In all cases, best professional judgement was used in determination of treatment. In order to post process the lidar data to meet task order specifications and meet ASPRS vertical accuracy guidelines, Woolpert established 42 ground control points that were used to calibrate the lidar to known ground locations established throughout the project area. An additional 165 independent accuracy checkpoints (89 NVA points and 76 VVA points), were collected and used to assess the vertical accuracy of the data. These checkpoints were not used to calibrate or post process the data.

This metadata record supports the data entry in the NOAA Digital Coast Data Access Viewer (DAV). For this data set, the DAV is leveraging the GeoTIFF files hosted by USGS on Amazon Web Services.

Data was collected to be used for the following: terrain mapping, conservation planning and design, support of easement/land stewardship programs, support of special emphasis programs, support of soil projects, fill gaps in existing lidar, water resource management.

USGS Contract No. G16PC00022 Task Order No. G16PD01047. CONTRACTOR: Woolpert Raster File Type = IMG Bit Depth/Pixel Type = 32-bit float Raster Cell Size = 1 Meter Interpolation or Re-sampling Technique = Triangulated Irregular Network Required Vertical Accuracy = 19.6 cm NVA

Any conclusions drawn from the analysis of this information are not the responsibility of NOAA, the Office for Coastal Management or its partners.

Data is available online for bulk and custom downloads

None

Users should be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no longer represent actual surface conditions. Users should not use this 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. The information contained in these data is dynamic and may change over time. The data are not better than the original sources from which they were derived. It is the responsibility of the data user to use the data appropriately and within the limitations of the data for which it was requested and prepared, in general, and these data in particular. Woolpert gives no warranty, expressed or implied, as to the accuracy, reliability, or completeness of these data. It is strongly recommended that these data are directly acquired from a Woolpert server, and not indirectly through other sources which may have changed the data in some way. Although these data have been processed successfully upon Woolpert's computer system, no warranty, expressed or implied, is made regarding the utility of the data on another system, or for general or scientific purposes; nor shall the act of distribution constitute any such warranty. This disclaimer applies both to individual use of the data and aggregate use with other data.

Microsoft Windows 10 Version 1607 (Build 14393.2189); ArcMap 10.3; ArcCatalog 10.3; TerraScan ver. 17; TerraModeler ver. 17; Geocue 2017.2.20.0.

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 non-vegetated land cover classes. This is a required accuracy. The NVA was tested with 89 checkpoints located in non-vegetated areas. 2. Vegetated Vertical Accuracy (VVA): VVA shall be reported for vegetated land cover classes. The target VVA is: 29.4 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 76 checkpoints located in vegetated areas. The checkpoints 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 Standard for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASRPS Guidelines.

Tested 0.074 meters NVA at a 95% confidence level using RMSE(z) 0.038 x 1.9600 as defined by the National Standard for Spatial Data Accuracy (NSSDA). The NVA of the DEM was calculated using 89 independent checkpoints located in non-vegetated land cover categories.

Tested 0.216 meters VVA was calculated using 76 checkpoints located in vegetated land cover categories at the 95th percentile, derived according to ASPRS Guidelines, Vertical Accuracy Reporting for Lidar Data. Tested against the DEM. VVA Errors larger than 95th percentile include: Point 3009_A, Easting 673096, Northing 4230152, Z-Error 0.323 Meters, Point 3035, Easting 652955, Northing 4245351, Z-Error 0.250 Meters, Point 3042_A, Easting 725087, Northing 4155090, Z-Error 0.314 Meters.

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 DEM is of good quality and data passes Non-Vegetated and Vegetated Vertical Accuracy specifications.

Data covers the entire area specified for this project.

Data is backed up to cloud storage.

The NOAA Office for Coastal Management (OCM) ingested references to the USGS GeoTIFF files that are hosted on Amazon Web Services (AWS), into the Digital Coast Data Access Viewer (DAV). The DAV accesses the raster data as it resides on AWS.