2020 USACE USGS Topobathy Lidar DEM: Cape May & Atlantic City, NJ

Create custom data files by choosing data area, map projection, file format, etc. A new metadata will be produced to reflect your request using this record as a base.

Bulk download of data files in the original coordinate system.

Entwine Point Tile (EPT) is a simple and flexible octree-based storage format for point cloud data. The data is organized in such a way that the data can be reasonably streamed over the internet, pulling only the points you need. EPT files can be queried to return a subset of the points that give you a representation of the area. As you zoom further in, you are requesting higher and higher densities. A dataset in EPT will contain a lot of files, however, the ept.json file describes all the rest. The EPT file can be used in Potree and QGIS to view the point cloud.

Link to view the point cloud (using the Entwine Point Tile (EPT) format) in the 3D Potree viewer.

The Data Access Viewer (DAV) allows a user to search for and download elevation, imagery, and land cover data for the coastal U.S. and its territories. The data, hosted by the NOAA Office for Coastal Management, can be customized and requested for free download through a checkout interface. An email provides a link to the customized data, while the original data set is available through a link within the viewer.

This graphic displays the footprint for this lidar data set.

Link to custom download, from the Data Access Viewer (DAV), the lidar point data from which these raster Digital Elevation Model (DEM) data were created.

These data were collected using the CZMIL system. It is owned and operated by the U.S. Army Corps of Engineers (USACE). The system collects topobathy lidar data at 10 kHz and RGB imagery at 2 Hz. A CASI-1500 hyperspectral line scanner is integrated with the system as well. Aircraft position, velocity and acceleration information are collected through a combination of NovAtel and POS A/V 610 equipment. All raw data streams are transferred to the office for downloading and processing in CZMIL's HydroFusion software. Aircraft position data are processed using POSPac software and the results are combined with the lidar data to produce 3-D positions for each lidar shot. Upon inspection and QA/QC in the software packages Fledermaus and PFM_ABE, anomalous data are flagged as invalid and have the withheld bit set.

LAS files are imported into TerraScan V13 module within MicroStation V8i, classifies valid topobathy data as ground points (2) and unclassified points (1), and valid bathymetric points (29). Upon completion the macro, the classification results undergo quality control and any misclassified points are manually edited. In areas of dense vegetation the bare earth ground points might be incorrectly classified due to the inability of the laser to penetrate the canopy and reach the bare ground. In these areas, JALBTCX defaults to the algorithm's "ground" surface instead of manually reclassifying those points. They are partitioned into a series of 1-km delivery boxes, one Classified LAS file per box. The format of the file is LAS version 1.2. Data are classified as 1 (valid non-ground topographic data), 2 (valid ground topographic data), and 29 (valid bathymetric data). Vertical positions are also transformed from ellipsoid to orthometric heights referenced to the North American Vertical Datum of 1988 (NAVD88). The files are then compressed with the open-source LASzip utility, which is part of the LAStools package (LAStools, "Efficient LiDAR Processing Software" (version 170923, unlicensed)), obtained from http://rapidlasso.com/LAStools.

Data classified as ground points (2) and bathymetric points (29) in the las files are converted to a grid by generating a triangulated irregular network (TIN) and then extracting the grid node elevations from the TIN surface. The origin point of the grid is located at a horizontal position whose value is evenly divisible by the 1m grid resolution such that rasters from subsequent surveys have common cell boundaries. JALBTCX uses Quick Terrain Modeler V8.2.1 to perform this operation utilizing the following parameters; "Legacy Triangulation", "Max Sample Excursion - 500", "Max Triangle Side "500", and "Tiling Settings Snap to Grid (Expand)." The grid is exported from Quick Terrain Modeler as a GeoTIFF 32-Bit DEM file. Utilizing an in-house python script within Jupyter Notebook, the null data values in the file are converted from -9999 to NoData with the Set Null tool from the ArcGIS Spatial Analyst Toolbox. The script also calls the Define Projection tool from the ArcGIS Data Management Toolbox to set the file's coordinate system information to "The North American Datum of 1983 (2011)." The raster is then multiplied against a corresponding 1m mask raster, an intermediate mask image produced from JALBTCX's 1mGrid data product, to remove interpolated areas where data does not exist. Horizontal positions, provided Universal Transverse Mercator Zone 18 North (NAD83 2011). Vertical positions are referenced to the NAD83 (2011) ellipsoid and provided in meters. The National Geodetic Survey's (NGS) GEOID12B model is used to transform the vertical positions from ellipsoid to orthometric heights referenced to the North American Vertical Datum of 1988 (NAVD88).

The NOAA Office for Coastal Management (OCM) received GeoTiff format files from USACE JALBTCX for the New Jersey coastline project area. The bare earth raster files were at a 1 m grid spacing. The data were in UTM Zone 18, (NAD83 2011), meters coordinates and NAVD88 (Geoid12B) elevations in meters. OCM assigned the appropriate EPSG codes (Horiz - 6347, Vert - 5703) and copied the raster files to https for Digital Coast storage and provisioning purposes.