2024 USGS Lidar DEM: Western MA

Original Product: These are Digital Elevation Model (DEM) data for Massachusetts as part of the required deliverables for the MA_Western_B24_WU300803 project. Class 2 (ground) LiDAR points in conjunction with the hydro breaklines were used to create a .5 meter hydro-flattened Raster DEM.

Original Geographic Extent: 14 counties in Massachusetts, covering approximately 3557 total square miles. The counties are: Bennington, Berkshire, Cheshire, Columbia, Dutchess, Franklin, Hampden, Hampshire, Hartford, Litchfield, Rensselaer, Tolland, Windham, Worcester

Original Dataset Description: The MA_Western_B24_WU300803 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. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base LiDAR Specification, 2024 Rev. A. The data were developed based on a horizontal projection/datum of NAD 1983 2011 UTM Zone 18N, Meter and vertical datum of NAVD88 Geoid 18, Meter. LiDAR data were delivered as processed Classified LAS 1.4 files formatted to 4095 individual 1500m x 1500m tiles, as tiled intensity imagery, and as tiled bare earth DEMs; all tiled to the same 1500m x 1500m schema. Continuous breaklines were produced in Esri file geodatabase format.

Ground Conditions: LiDAR was collected in spring 2024, 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, NV5 Geospatial utilized a total of 38 ground control points that were used to calibrate the LiDAR to known ground locations established throughout the project area. An additional 156 independent accuracy checkpoints, 124 in Bare Earth and Urban landcovers (124 NVA points), 32 in Tall Weeds categories (32 VVA points), were 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.

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 high accuracy 3D hydro-flattened digital elevation models (DEMs) with a .5 meter cell size. These raw LiDAR point cloud data were used to create classified LiDAR LAS files, intensity images, 3D breaklines, and hydro-flattened DEMs as necessary.

Raster File Type = GeoTIFF; Bit Depth/Pixel Type = 32-bit float; Raster Cell Size = .5 meter; Interpolation or Resampling Technique = Triangulated Irregular Network (TIN), Linear Interpolation, Proprietary; Required Vertical Accuracy = 0.196

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.

This data set was produced to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a 81 (cm) RMSEr Horizontal Accuracy Class which equates to Positional Horizontal Accuracy = +/- 141 cm at a 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 cm RMSE

Vegetated Vertical Accuracy (VVA) = 20.68 cm at the 95th Percentile

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 raw point cloud is of good quality and data pass Non-Vegetated Vertical Accuracy specifications.

Data cover 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.