2017 CA DWR Lidar DEM: Sacramento Delta, CA

Dataset Description: The CA Central Valley Lidar 2016 D16 Mod 002: CA Sacramento Delta Lidar 2017 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 0.35 meters. Project specifications were based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 1.2

Ground Conditions: Lidar was collected from December 9, 2017 through January 21, 2018 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. Intermittently, partially flooded, irregular, and apparently non-agricultural fields were treated as 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 35 ground control points that were used to calibrate the lidar to known ground locations established throughout the project area. An additional 143 independent accuracy checkpoints (75 NVA points and 68 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.

In addition to these bare earth Digital Elevation Model (DEM) data, the lidar point data that these DEM data were created from, are also available. These data are available for custom download at the link provided in the URL section of this metadata record.

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 (Mod 002). CONTRACTOR: Woolpert

Raster File Type = IMG

Bit Depth/Pixel Type = 32-bit float

Raster Cell Size = 0.5 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.

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 68 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 68 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 0.099 meters NVA at a 95% confidence level using RMSE(z) 0.051 x 1.9600 as defined by the National Standard for Spatial Data Accuracy (NSSDA). The NVA of the DEM was calculated using 75 independent checkpoints located in non-vegetated land cover categories.

Tested 0.289 meters VVA was calculated using 68 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 3001, Easting 576285.632, Northing 4229651.745, Z-Error 0.386 Meters

Point 3039_A, Easting 613532.538, Northing 4217704.581, Z-Error 0.313 Meters

Point 3044, Easting 636454.834, Northing 4187011.525, Z-Error 0.301 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.

This data set was downloaded from the CA DWR ftp site and processed to make it available for custom download from the Data Access Viewer (DAV) and for bulk download from https.