2024 USGS Lidar DEM: New York & New Hampshire Gaps

Original Product: These lidar data are processed Quality Level 2 (QL2) Bare-Earth DEM files, formatted to individual 1500 m x 1500 m tiles at 1 meter resolution.

Original Dataset Geographic Extent:

New York - One area covers 2284 sq miles

New Hampshire - Two separate areas one that is 125 sq miles and the other 462 sq miles in area totaling 587 sq miles.

Original Dataset Description: The New York and New Hampshire Gaps Lidar project called for the Planning, Acquisition, processing and derivative products of lidar data to be collected at a nominal point density of 2 points per square meter for QL2 data. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification 2024, 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 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 2024, while no snow was on the ground.

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.

This task is for providing a spring 2024 leaf-off and snow-free lidar survey over an area of approximately 2,872 square miles. This project will support the 3DEP mission, the Natural Resources Conservation Service (NRCS) high-resolution elevation enterprise, as well as many state and local agencies.

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 DEMs. The purpose of these LiDAR data was to produce an auto generated elevation models (DEMs) with a 1 meter cell size.

Raster File Type = TIFF Bit Depth/Pixel Type = 32-bit float Raster Cell Size = 1 Meter Interpolation or Resampling Technique = Triangulated Irregular Network Required Vertical Accuracy = 19.6 cm NVA

No limits or restrictions. 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.

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 2286 meters, an IMU error of 0.0025 decimal degrees, and a GNSS positional error of 0.05 meters, this project was compiled to meet 0.55 meter horizontal accuracy at 95% confidence level.

This data set was produced to meet ASPRS Positional Accuracy Standard for Digital Geospatial Data (2023) Ed 1.0 for a 10-cm RMSEz Vertical Accuracy Class.

USGS Determined DEM Vertical Accuracy:

Non-Vegetated Vertical Accuracy (NVA) = 5.84 cm RMSE

Vegetated Vertical Accuracy (VVA) = 15.9 cm at the 95th Percentile

The dataset was reviewed to ensure completeness and accuracy.

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.