2025 CBNERRVA Lidar DEM: Catlett Islands, Goodwin Islands, Sweet Hall Marsh, Taskinas Creek, VA

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 GeoTIFF format, projected coordinates, orthometric heights. Note that the vertical datum (hence elevations) of the files here are different than described in this document. They will be in an orthometric datum.

Link to download the breaklines in ESRI gdb and OGC GeoPackage formats.

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.

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

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.

The boresight was completed prior to project execution. The following steps describe the Raw Data Processing process:

1) Technicians processed the raw data to LAS format flight lines using the final GNSS/IMU solution. This LAS data set was used as source data for lidar matching.

2) Technicians utilized commercial and proprietary software packages to analyze how well flight line overlaps match for the entire lift and adjusted as necessary until the results met the project specifications.

3) Once all lifts were completed with lidar matching, the technicians checked and corrected the vertical misalignment of all flight lines and also the matching between data and ground truth. The relative accuracy was less than or equal to 6 cm RMSEz within individual swaths and less than or equal to 8 cm RMSEz or within swath overlap (between adjacent swaths).

4) The technicians ran a final vertical accuracy check of the flight lines against the surveyed check points after the z correction to ensure the requirement of NVA = 19.6 cm 95% Confidence Level (Required Accuracy) was met. Point classification was performed according to USGS Lidar Base Specification, and breaklines were collected for water features. Bare-earth DEMs were exported from the classified point cloud using collected breaklines for hydroflattening.

LAS Point Classification: The point classification is performed as described below:

Bare-earth points are extracted from the point cloud using automated processes in Terrascan. Then the bare-earth surface is manually reviewed to ensure correct classification on the Class 2 (Ground) points. All points determined to be in water are then classified to Class 9 (Water). No overlap points were classified or flagged, and all withheld points were flagged using Terrascan. All data was manually reviewed and any remaining artifacts removed using functionality provided by LP360, TerraScan and TerraModeler. Global Mapper was used as a final check of the bare-earth dataset. GeoCue was then used to create the deliverable industry-standard LAS files. Sanborn Map Company, Inc. uses proprietary software to perform final statistical analysis of the classes in the LAS files, on a per tile level to verify final classification metrics and full LAS header information.

Data was tested at 0.26 meter aggregate nominal pulse spacing and at 14.8 aggregate points per meter. The aggregate nominal pulse spacing was tested on classified tiled LAS using geometrically reliable first-return points without overlap. ANPS was tested using Delaunay Triangulation that produced average point spacing between all nearest neighbors.

Maximum Surface Height Rasters were produced as ancillary data from the classified lidar point cloud in order to evaluate the withheld bit flag proof of performance for points that cannot be reasonably interpreted as valid surface returns. These were produced using all returns, withheld flagged points excluded, and using the highest elevation point value from each pixel. These rasters are 32-bit, floating point format and delivered as GeoTIFF files per tile. Cell size of the MSHR is 2 ft. MSHR are generated from the point cloud data and will not be altered after creation nor will there be further maintenance on this product.

Swath Separation Imagery was produced for the entire project area. Swath separation images use color-coding to illustrate differences in elevation (z-) values where swaths overlap. The color-coded images are semi-transparent and overlay the lidar intensity image. They are ancillary data used as visual aids to more easily identify regions within point cloud datasets that may have suspect interswath alignment or other geometric issues. Imagery was created using last returns with all classification and bit flags, except for noise and withheld bit flag are included. Images are derived from a TIN and have a 50% transparent RGB layer over lidar intensity. Color intervals are as follows: 0-8cm, green; 8-16cm, yellow; >16cm, red. These files were produced as GeoTIFF tiles using a cell size of 2 ft. SSI are generated from the point cloud data and will not be altered after creation nor will there be further maintenance on this product.

Bare-earth DEM Process: Class 2 (Ground) lidar points were used to create a 1 ft Raster DEM. Using automated scripting routines within LP360, a GeoTIFF file was created for each tile. Each surface is reviewed using Global Mapper to check for any surface anomalies or incorrect elevations found within the surface.

The NOAA Office for Coastal Management (OCM) received 132 GeoTIFF files from the Chesapeake Bay NERR (CBNERRVA). The files were in VA State Plane South NAD83(HARN), US feet coordinates and the elevations were in NAVD88 (GEOID18) US feet. The bare earth raster files were at a 1 ft grid spacing. OCM assigned the vertical EPSG code (6360), the horizontal EPSG code (2925) and copied the raster files to AWS S3 for Digital Coast storage and provisioning purposes.

The RIEGL VQ-1560 II-S system has a rotating mirror design and high-output dual laser technology, allowing for data collection at a higher altitude and faster speed on large-scale mapping projects and corridor work. This system provides more dense, high-precision data with uniform point distribution and faster acquisition.