Data Management Plan

Product: QL2 LAS 1.4

Geographic Extent: This NIR Lidar dataset and derived products encompass an area covering approximately 473,860 acres of South East Alaska. The Quality Level 2 (QL2) project area encompassed 345,212 acres of the total area.

Dataset Description :The Glacier Bay 3DEP Lidar project called for the planning, acquisition, and processing of Lidar data collected at an aggregate nominal pulse spacing (ANPS) of 0.71 meters for all QL2 areas. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 1.3. The data was developed based on the NAD83(2011) horizontal datum and NAVD88 (GEOID12B) vertical datum. Data was projected in UTM Zone 8N. All units are in meters. RAW flight line swaths were processed to create 2,390 classified LAS 1.4 files delineated in 1,000 m x 1,000 m tiles. Please note that tiles GB_03743 and GB_05552 do not include valid point return data as they are entirely over areas of open water and thus have not been included in this submission. Each LAS file contains Lidar point information, which has been calibrated, controlled, and classified. Additional derived products include hydro-flattened DEMs, Highest Hit DSMs, Intensity Images, DZ Orthos, Flightline Shapes, Swath Coverage Shapes, Ground Survey Shapes and 3D breaklines of rivers and lakes within the study area.

Ground Conditions: Lidar was collected in summer 2019, while the presence of snow on the ground was at a minimum 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, DOWL on behalf of QSI established a total of 194 ground control points distributed throughout the Glacier Bay Delivery 1 project area. Lidar data was calibrated to these known ground locations. An additional 115 independent accuracy checkpoints, 33 in Bare Earth and Urban landcovers (NVA points) and 82 in Shrub, Tall Grass, and Forest categories (VVA points) were used to assess the vertical accuracy of the project data. These checkpoints were not used to calibrate or post process the data.

Note: currently only Delivery 1 of 2 has been released (Blocks 2 & 3, collected in 2019). When the second and final delivery is made available NOAA OCM will incorporate the data and update this metadata record.

Process Steps:

• 2020-05-04 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 correction. 5. Import raw laser points into manageable blocks to perform manual relative accuracy calibration and filter erroneous points. Classify ground 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.
• 2020-05-04 00:00:00 - 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 NVA and VVA, and density information for the project using ground control quality check points. For Ql1 areas single swath nominal pulse spacing (NPS) was designed to be 0.50 at nadir and the aggregate Nominal Pulse Spacing (ANPS) was calculated to be 0.31 using all valid first return points.
• The NOAA Office for Coastal Management (OCM) downloaded this data set from this USGS site: ftp://rockyftp.cr.usgs.gov/vdelivery/Datasets/Staged/Elevation/LPC/Projects/AK_GlacierBay_2019_B19/ The data were in UTM Zone 8 North (NAD83 2011) coordinates and NAVD88 (Geoid12B) elevations in meters. The data were classified as: 1 - Unclassified, 2 - Ground, 7 - Low Noise, 9 - Water, 17 - Bridge Decks, 18 - High Noise, 20 - Ignored Ground, 22 - Temporal Exclusion. OCM processed all classifications of points to the Digital Coast Data Access Viewer (DAV). OCM performed the following processing on the data for Digital Coast storage and provisioning purposes: 1. An internal OCM script was run to check the number of points by classification and by flight ID and the gps and intensity ranges. 2. Internal OCM scripts were run on the laz files to convert from orthometric (NAVD88) elevations to ellipsoid elevations using the Geoid 12B model, to convert from UTM Zone 8 North (NAD83 2011) coordinates in meters to geographic coordinates, to assign the geokeys, to sort the data by gps time and zip the data to database and to http.

Data is available online for bulk or custom downloads

Data is backed up to tape and to cloud storage.