2017 - 2018 USGS Lidar DEM: NW New Jersey 6 County

Original Dataset Product: Bare earth Digital Elevation Model (DEM) data.

Original Dataset Geographic Extent: 6 counties, New Jersey, covering approximately 2,358 square miles.

Original Dataset Description: Sussex, Passaic, Warren, Morris, Hunterdon, Somerset county, New Jersey 2018 Lidar project called for the Planning, Acquisition, processing and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.7 meter. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 1.3. The data was developed based on a horizontal projection/datum of NAD83 (2011), State Plane New Jersey, feet and vertical datum of NAVD88 (GEOID12B), feet. Lidar data was delivered as processed Classified LASv1.4 files, formatted to 2,843 individual 5,000 ft x 5,000 ft tiles, as tiled intensity imagery, and as tiled bare-earth DEMs; all tiled to the same 5,000 ft x 5,000 ft schema.

Original Dataset Ground Conditions: Lidar was collected in early 2017 and 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, The Sanborn Map Company, Inc. established a total of 30 ground control points that were used to calibrate the lidar to known ground locations established throughout the project area. An additional 140 independent accuracy check points, 79 in Open Terrain/Bare-Earth and Urban landcovers (79 NVA points), 61 in Grass, Brush and Trees categories (61 VVA points), were used to assess the vertical accuracy of the data. These check points 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 2 ft 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 = IMG Bit Depth/Pixel Type = 32-bit float Raster Cell Size = 2 feet Interpolation or Resampling 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.

The project specifications require that only Non-Vegetated Vertical Accuracy (NVA) be computed for raw lidar point cloud swath files. The required accuracy (ACCz) is: 19.6 cm at a 95% confidence level, derived according to NSSDA, i.e., based on RMSE of 10 cm in the bare earth and urban land cover classes. The NVA was tested with 79 checkpoints located in open terrain/bare earth and urban (non-vegetated) areas. These check points were not used in the calibration or post processing of the lidar point cloud data. The check points were distributed throughout the project area and were surveyed using GPS techniques. Elevations from the unclassified lidar surface were measured for the x,y location of each check point. Elevations interpolated from the lidar surface were then compared to the elevation values of the surveyed control points. 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.

Sanborn Determined DEM Vertical Accuracy:

NVA = 7.8 cm RMSE

VVA = 10.8 cm at 95th Percentile

USGS Determined DEM Vertical Accuracy:

NVA = 8 cm RMSE

VVA = 11.77 cm at 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 passes Non-Vegetated Vertical Accuracy specifications.

Data covers the AOI specified for this project.

Data is backed up to tape and to cloud storage.

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.