Data Management Plan

Product: Classified LAS 1.4 files, formatted to 85 individual 1,000m x 1,000m covering the Nisqually River Basin 2020 project area.

Geographic Extent: This dataset and derived products encompass an area covering approximately 13,189 acres of Western Washington.

Dataset Description: The Nisqually River Basin 2020 Lidar project called for the planning, acquisition, and processing of topobathy Lidar data collected to Quality Level 1 (QL1) standards. Project specifications are based on the U.S. Geological Survey National Geospatial Program LIDAR Base Specification, Version 2.1. The data was developed based on the NAD83 2011 horizontal datum and the NAVD88 Geoid 18 vertical datum. Data was projected in UTM Zone 10. Lidar data was delivered as calibrated and classified LAS 1.4 files. Non-Vegetated Vertical Accuracy (NVA) was assessed using 22 check points located on bare earth in clear, unobstructed areas. Submerged Topography accuracy was assessed using 86 check points collected as feasible in depths up to 1m. Vegetated Vertical Accuracy (VVA) was assessed using 14 check points in tall grass, forest, and shrubland landcover types. Single swath nominal pulse spacing (NPS) was designed to be 9.5 points per meter squared at nadir. Aggregate Nominal Pulse Spacing (ANPS) was calculated to be 36.59 points per meter squared using all valid first return points. Derived products include: Intensity Imagery, Topbathymetric Digital Elevation Models (DEMs), Hydro-flattened Bare Earth Digital Elevation Models (DEMs), Highest Hit Digital Surface Models (DSMs), 3D waters edge breaklines, and a bathymetric coverage shape.

Ground Condition: Ground condition was free of snow and acquisition occurred free of smoke, fog and cloud cover.

This metadata supports the data entry in the NOAA Digital Coast Data Access Viewer (DAV). For this data set, the DAV is leveraging the Entwine Point Tiles (EPT) hosted by USGS on Amazon Web Services.

Lineage Statement:
The Nisqually River Basin lidar was ingested into the Data Access Viewer for custom product generation by leveraging USGS hosted Entwine Point Tiles.

Process Steps:

• 2021-03-30 00:00:00 - 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 18 correction.5. Apply refraction correct to bathymetric returns by flightline.6. Import raw laser points into manageable blocks to perform manual relative accuracy calibration and filter erroneous points. Classify ground points for individual flight lines.7. 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.8. Adjust the point cloud by comparing ground classified points to supplemental ground control points.
• 2021-03-30 00:00:00 - Lidar Post-Processing:1. Classify data to ground and other client designated classifications using proprietary classification algorithms.2. Manually QC data classification3. After completion of classification and final QC approval, calculate final NVA, VVA, and density information for the project using ground control quality check points.
• 2021-03-30 00:00:00 - Breaklines: Water boundary polygons were developed using an algorithm which weights lidar-derived slopes, intensities, and return densities to detect the water's edge. The water's edge was then manually reviewed and edited as necessary.
• 2021-03-30 00:00:00 - Bathymetric Coverage Shape: Insufficiently mapped areas were identified by triangulating bathymetric bottom points with an edge length maximum of 4.56 meters. This shape was used to clip the final topobathymetric DEMs to avoid interpolation over areas lacking bathymetric returns.
• Original point clouds in LAS/LAZ format were restructured as Entwine Point Tiles and stored on Amazon Web Services. The data were re-projected horizontally to WGS84 Web Mercator (EPSG 3857). Vertically, the data were converted to meters and no changes were made to the vertical datum (NAVD88 GEOID18; EPSG 5703).
• 2022-05-02 00:00:00 - References to the entwine point tiles and data reports were ingested into the Digital Coast Data Access Viewer. No changes to the data were made at this point. The Data Access Viewer will access the point cloud as it resides on AWS under the usgs-lidar-public container.

Data is available online for bulk and custom downloads.

Data is backed up to tape and to cloud storage.