Data Management Plan

A digital elevation model (DEM) mosaic was produced for Assateague Island, Maryland and Virginia, post-Hurricane Hermine, from remotely sensed, geographically referenced elevation measurements collected by Quantum Spatial using a Riegl VQ-880-G (532-nm wavelength circular scan and 1064-nm wavelength linear scan) lidar sensor.

Lineage Statement:
Quantum Spatial acquired and processed topobathy lidar data to DEMs. USGS combined the individual DEM tiles into a single GeoTiff. NOAA updated the georeferencing information and created a cloud optimized GeoTiff.

Process Steps:

• 2016-11-30 00:00:00 - Quantum Spatial reports the following steps for Lidar Pre-Processing: 1. Review flight lines and data to ensure complete coverage of the study area and positional accuracy of the laser points. 2. Resolve kinematic corrections for aircraft position data using kinematic aircraft GPS and static ground GPS data. 3. Develop a smoothed best estimate of trajectory (SBET) file that blends post-processed aircraft position with sensor head position and attitude recorded throughout the survey. 4. Calculate laser point position by associating SBET position to each laser point return time, scan angle, intensity, etc. Create raw laser point cloud data for the entire survey in *.las format. Convert data to orthometric elevations by applying a geoid correction. 5. Import raw laser points into manageable blocks to perform manual relative accuracy calibration and filter erroneous points. Apply the refraction correction necessary for bathymetric data. Classify ground/bathymetric points for individual flight lines. 6. Using ground classified points per each flight line, test the relative accuracy. Perform automated line-to-line calibrations for system attitude parameters (pitch, roll, heading), mirror flex (scale) and GPS/IMU drift. Calculate calibrations on ground classified points from paired flight lines and apply results to all points in a flight line. Use every flight line for relative accuracy calibration. 7. Adjust the point cloud by comparing ground classified points to supplemental ground control points.
• 2016-11-30 00:00:00 - Quantum Spatial reports the following steps for Lidar Post-Processing: 1. Classify data to ground and other client designated classifications using proprietary classification algorithms. 2. Manually QC data classification 3. After completion of classification and final QC approval, calculate density information and verify final accuracy calculations for the project using ground control quality check points.
• 2016-11-30 00:00:00 - Quantum Spatial reports the following steps for Breaklines: Water boundary polygons were developed using manual editing techniques. Elevations were assigned to the water’s edge from the LiDAR point cloud data. Breaklines were also used to classify water surface (class 41).
• 2016-11-30 00:00:00 - Quantum Spatial reports the following steps for Bathymetric Coverage: Bathymetric coverage was determined by triangulating bathymetric points (class 40) with and edge length maximum of 4.56m to identify all areas >9m2 lacking bathymetric data. This shapefile was used to control the extent of the topobathymetric DEMs.
• 2016-12-28 00:00:00 - The provided DEM .IMG files were mosaicked using Global Mapper 16 (20160309) and exported as a GeoTIFF.
• 2019-06-25 00:00:00 - The merged GeoTiff file was received from USGS by NOAA OCM. The georeferencing codes were changed to reflect NAD83(2011) and NAVD88 instead of generic NAD83. Coordinates were not changed. The GeoTiff was processed to a cloud optimized GeoTiff (COG) using GDAL version 2.4.1.

Data is available online for custom downloads