2023 USGS Lidar DEM: DE Statewide & MD (Caroline, Dorchester, Kent, and Talbot Counties)

Original Product: These lidar data are processed Quality Level 1 (QL1) Bare-Earth DEM files, formatted to 4791 individual 1500 m x 1500 m tiles at 0.5 meter resolution.

Original Dataset Geographic Extent: The state of Delaware and four counties of Maryland, including Kent, Talbot, Caroline, and Dorchester counties.

Original Dataset Description: The Delaware 2023, Work Unit 300433 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 for QL1 data. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification 2023, revision A.

The data was developed based on a horizontal projection/datum of NAD83 (2011), UTM 18N, meters and vertical datum of NAVD88 (GEOID18), meters. Lidar data was delivered as processed Classified LAS 1.4 files, formatted to 4779 individual 1500 m x 1500 m tiles and as tiled bare earth DEMs; all tiled to the same 1500 m x 1500 m schema.

Ground Conditions: Lidar was collected in the spring 2023, while no snow was on the ground and waterways were at low tide.

In order to post process the lidar data to meet task order specifications and meet ASPRS vertical accuracy guidelines, a total of 197 checkpoints were used to calibrate the lidar to known ground locations established throughout the project area. A total of 110 Non-Vegetated Vertical Accuracy (NVA) points were used. A total of 87 Vegetated Vertical Accuracy (VVA) points were used. 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.

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 0.5 meter cell size for QL1 data.

USGS Contract No. 140G0223F0125 CONTRACTOR: SAM

Lidar data were acquired and calibrated by SAM. All follow-up processing was completed by the prime contractor.

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.

VQ-1560i; TerraScan v22.007; TerraModel v22.06; Global Mapper Pro v24; Windows 10 Pro

LiDAR horizontal accuracy is a function of Global Navigation Satellite System (GNSS) derived positional error, flying altitude, and INS derived attitude error. The obtained RMSEr value is multiplied by a conversion factor of 1.7308 to yield the horizontal component of the National Standards for Spatial Data Accuracy (NSSDA) reporting standard where a theoretical point will fall within the obtained radius 95% of the time. Based on a flying altitude of 1372 meters, an IMU error of 0.0025 decimal degrees, and a GNSS positional error of 0.05 meters, this project was compiled to meet 0.08 meter horizontal accuracy at 95% confidence level.

This data set was produced to meet ASPRS Positional Accuracy Standard for Digital Geospatial Data (2014) for a 10-cm RMSEz Vertical Accuracy Class.

USGS Determined DEM Vertical Accuracy:

Non-Vegetated Vertical Accuracy (NVA) = 4.19 cm RMSE

Vegetated Vertical Accuracy (VVA) = 13.02 cm at the 95th Percentile

These Bare-Earth DEMs were created using all ground points included in the LAS data files. No points have been removed or excluded. A visual qualitative assessment was performed to ensure data completeness. No void areas or missing data exist. The Bare-Earth DEMs are of good quality and data passes Non-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.