Data Management Plan

Original Dataset Product: These are Digital Elevation Model (DEM) data delivered as part of the Louisiana Breton topobathy lidar project. Class 2 (ground) and class 40 (bathymetry) lidar points were used to create a 0.5-meter merged topo-bathy DEM.

Original Dataset Geographic Extent: Breton, Louisiana, covering approximately 129.4 square miles.

Original Dataset Description: The Louisiana Breton Topobathymetric Lidar project called for the planning, acquisition, processing and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.35 meters (QL1) for topographic areas and 0.71 meter (QL2b) for bathymetric areas. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, 2024 rev A. The data was developed based on a horizontal projection/datum of NAD83 (2011), UTM zone 16N, meters and vertical datum of NAVD88 (Geoid 18), meters. Lidar data were delivered as processed Classified LAS 1.4 files, formatted to 1570 individual 500 m x 500 m tiles, as tiled Intensity Imagery, and as tiled topobathymetric DEMs; all tiled to the same 500 m x 500 m schema.

Original Dataset Ground Conditions: Lidar was collected from October 6, 2022 to November 3, 2022, 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, Dewberry established 17 ground control points (GCP) and 5 bathymetric control points (BCP) that were used to calibrate the lidar to known ground positions established throughout the project area. An additional 27 independent accuracy checkpoints--20 in bare earth and urban land cover (NVA), 7 in submerged topography land cover (BVA)--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 USGS GeoTIFF files hosted by USGS on Amazon Web Services.

Lineage Statement:
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.

Process Steps:

• 2024-03-28 00:00:00 - The boresight for each lift was done individually as the solution may change slightly from lift to lift. The following steps describe the Raw Data Processing and Boresight process: 1) Technicians processed the raw data to LAS format flight lines using the final GPS/IMU solution. This LAS data set was used as source data for boresight. 2) Technicians first used proprietary and commercial software to calculate initial boresight adjustment angles based on sample areas selected in the lift. These areas cover calibration flight lines collected in the lift, cross tie and production flight lines. These areas are well distributed in the lift coverage and cover multiple terrain types that are necessary for boresight angle calculation. The technician then analyzed the results and made any necessary additional adjustment until it is acceptable for the selected areas. 3) Once the boresight angle calculation was completed for the selected areas, the adjusted settings were applied to all of the flight lines of the lift and checked for consistency. The 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. 4) Once all lifts were completed with individual boresight adjustment, 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). 5) The technicians ran a final vertical accuracy check of the boresighted 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 2024 rev A. Bare earth DEMs were exported from the classified point cloud.
• 2024-04-05 00:00:00 - Dewberry used algoritms in TerraScan to create the intial ground/submerged topography surface. Dewberry used rasterized aggregate extents of refracted points to create automated 2-D breaklines with LAStools and ArcGIS. Light travels at different speeds in air versus water and its speed and direction of travel change when it enters the water column. The refraction correction process accounts for this difference by adjusting the depth (distance traveled) and horizontal position (change of angle/direction) of the lidar points acquired within water. These breaklines delineate areas where the refraction correction was applied to the lidar data by Dewberry proprietary refraction correction tool. Dewberry used the 2-D refraction extents and additional bathy features to classify the bathymetric bottom and ground points properly in TerraScan. The withheld bit was set on class 7 and class 18 in TerraScan after all classification was complete. All lidar data was peer-reviewed. Dewberry's QAQC also included creating void polygons for use during review. All necessary edits were applied to the dataset. LASTools software was used to update LAS header information, including all projection and coordinate reference system information. The final lidar data are in LAS format 1.4 and point data record format 6. All data was then verified by an Independent QC department within Dewberry. The independent QC was performed by separate analysts who did not perform manual classification or editing. The independent QC involved quantitative and qualitative reviews.
• 2024-04-05 00:00:00 - Data was tested at 0.30 meter nominal pulse spacing and 11.02 points per square meter (ppsm). The average density was tested on the LAS data using geometrically reliable (withheld and noise points excluded) first-return points. (A)NPD was tested using rasters which produce the average number of points within each cell.
• 2024-04-05 00:00:00 - Digital elevation models were created using only ground (2) and submerged topography (40) lidar point data. A triangulated irregular network (TIN) was generated from these data and rasterized at a 0.5 m spatial resolution using the LAStools 'blast2dem' utility. Void polygons delineating areas of extremely sparse or non-existent bathymetric coverage were used in ArcGIS to clip large areas of interpolation in the DEM. The void polygon creation process is described in the void polygon metadata and final project report.
• 2024-04-07 00:00:00 - DEMs were reviewed using Global Mapper and ArcGIS to check for surface anomalies, incorrect elevations, and unacceptable voids in the data.
• 2024-12-06 00:00:00 - The NOAA Office for Coastal Management (OCM) created references to the USGS GeoTIFF files that were ingested into the NOAA Digital Coast Data Access Viewer (DAV). No changes were made to the data. The DAV will access the raster data as it resides on Amazon Web Services (AWS). This is the location of the GeoTIFF files that are being accessed: https://prd-tnm.s3.amazonaws.com/index.html?prefix=StagedProducts/Elevation/OPR/Projects/LA_BretonIslandTB_D22/LA_BretonIsl_Topobathymetric_D22/TIFF/

Data is available online for bulk and custom downloads.

Data is backed up to cloud storage.