2018 USGS Lidar DEM: Delaware County, OH

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

Original Dataset Geographic Extent: Covers approximately 439 square miles across Delaware County.

Original Dataset Description: The OH Clinton Delaware 2018 B18 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 0.71 meters. Project specifications were based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 1.3. The data was developed based on a horizontal datum/projection of NAD83 (2011) Contiguous USA Albers, Meters, and a vertical datum of NAVD88 (GEOID12B), Meters. DEM data was delivered as processed ERDAS IMG files formatted to 1,261 individual 1,000-meter x 1,000-meter tiles.

Ground Conditions: Lidar was collected by Woolpert in a total of 4 missions from March 6, 2018 through December 11, 2018, 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, Woolpert established 9 ground control points that were used to calibrate the lidar to known ground locations established throughout the project area. An additional 60 independent accuracy checkpoints (35 NVA points and 25 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. Note: There was flooding present in an area around Delaware Lake.

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 as part of this task order 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. G16PC0022; Task Order No. 140G0218F0168; 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.

To the extent possible under law, the U.S. Government has waived all copyright and related or neighboring rights to this dataset.

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 10.4; ArcCatalog 10.4; TerraModeler ver. 18; Geocue 2017.2.20.0, POSPac Software v. 5.3, IPAS Pro v.1.35, Novatel Inertial Explorer v8.60.6129, TerraMatch v.18.03, Leica Cloud Pro v1.2.3, TerraScan v.18.18

Not provided

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 35 checkpoints located in non-vegetated areas. 2. Vegetated Vertical Accuracy (VVA): VVA shall be reported for vegetated land cover classes. The target VVA is: 30 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 25 checkpoints located in vegetated areas. The checkpoints were distributed throughout the project area and were surveyed using GPS techniques. 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.

Tested 0.054 meters NVA at a 95% confidence level using RMSE(z) 0.028 meters x 1.9600 as defined by the National Standards for Spatial Data Accuracy (NSSDA). The NVA of the DEM was calculated using 35 independent checkpoints located in non-vegetated land cover categories.

Tested 0.201 meters VVA was calculated using 25 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 3004, Easting 1095281.875, Northing 1995606.127, Z-Error 0.256 Meters

Point 3016, Easting 1112147.216, Northing 1995286.821, Z-Error 0.210 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.

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.