Data Management Plan

Lidar-derived elevation data for Wrangell Island, Southeast Alaska, collected July 2023, Raw Data File 2023-28, provides lidar-derived classified point cloud, a digital surface model (DSM), a digital terrain model (DTM), and an intensity model of Wrangell Island, Southeast Alaska, during leaf-on ground conditions. The survey provides snow-free surface elevations for use in shoreline development, resource quantification, hydrographic mapping, and slope stability modeling. Ground control data were collected June 26-30, 2023, and aerial lidar data were collected July 7-11, 2023, and subsequently merged and processed using a suite of geospatial processing software. All files can be downloaded from the Alaska Division of Geological & Geophysical Surveys website (http://doi.org/10.14509/31098).

This metadata record supports the data entry in the NOAA Digital Coast Data Access Viewer (DAV).

The NOAA Office for Coastal Management (OCM) downloaded 1 GeoTiff data file from the AK DGGS (Alaska Division of Geological and Geophysical Surveys) from https://dggs.alaska.gov/webpubs/data/rdf2023_028_lidar-wrangell-2023-dtm-merged-only.zip . The data were processed to the NOAA Digital Coast Data Access Viewer (DAV) to make the data available for bulk and custom downloads.

In addition to these bare earth Digital Elevation Model (DEM) data, the lidar point data that these DEM data were created from are also available from the NOAA Digital Coast. A link to these data is provided in the URL section of this metadata record.

Lineage Statement:
Data were collected by the Alaska Division of Geological and Geophysical Surveys (AK DGGS). The data were downloaded by the NOAA Office for Coastal Management (OCM) and processed to make it available for custom download from the NOAA Digital Coast Data Access Viewer (DAV) and for bulk download from S3 AWS.

Process Steps:

• 2023-06-30 00:00:00 - Ground survey - Ground control points were collected June 26-30, 2023, by the Alaska Division of Mining, Land and Water (DMLW). They deployed a Trimble R12 GNSS receiver to provide a base station occupation and real-time kinematic (RTK) corrections to points they surveyed with a rover Trimble R12i GNSS receiver/TSC5 controller. Benchmark HH-2 (PID BBDX58), located on the Heritage Harbor breakwater in Wrangell, served as the base station location. DMLW collected 43 ground control points and 214 checkpoints to use for calibration and assess the vertical accuracy of the point cloud. Checkpoints were collected in forest, shrubland, grassland, sphagnum bog, bare earth, and paved surfaces. We processed and delivered all data in NAD83 (2011) UTM8N and vertical datum NAVD88 GEOID12B.
• 2023-07-11 00:00:00 - Aerial photogrammetric survey - DGGS used a Riegl VUX1-LR22 laser scanner integrated with a global navigation satellite system (GNSS) and Northrop Grumman LN-200C inertial measurement unit (IMU) designed by Phoenix LiDAR Systems. The sensor can collect a maximum of 1,500,000 points per second at a range of 150 m, or a minimum of 50,000 points per second at a range of 640 m. The scanner operated with a pulse refresh rate of 600,000 pulses per second over forested terrain, and 200,000 pulses per second over alpine terrain, with a scan rate between 50 and 200 lines per second. We used a Cessna 180 fixed-wing platform to survey from an elevation of approximately 150-350 m above ground level, at a ground speed of approximately 40 m/s, and with a scan angle set from 80 to 280 degrees. The total survey area covers approximately 565 km2. The survey area was accessed by air from Wrangell Airport. See table 1 of the accompanying report for data collection start and end times, and weather conditions.
• 2023-01-01 00:00:00 - Lidar dataset processing - We processed point data in Spatial Explorer for initial filtering and multiple-time-around (MTA) disambiguation. MTA errors, corrected in this process, result from ambiguous interpretations of received pulse time intervals and occur more frequently with higher pulse refresh rates. We processed IMU and GNSS data in Inertial Explorer, and flightline information was integrated with the point cloud in Spatial Explorer. We calibrated the point data at an incrementally precise scale of sensor movement and behavior, incorporating sensor velocity, roll, pitch, and yaw fluctuations throughout the survey. We created macros in Terrasolid software and classified points in accordance with the American Society for Photogrammetry & Remote Sensing (ASPRS) 2019 guidelines (ASPRS, 2019). Once classified, we applied a geometric transformation and converted the points from ellipsoidal heights to GEOID12B (Alaska) orthometric heights. We used ArcGIS Pro to derive raster products from the point cloud. A 50-cm DSM was interpolated from maximum return values from ground, vegetation, bridge deck, and building classes using a binning method and maximum values. A 50-cm DTM was interpolated from all ground class returns using a binning method and minimum values. We also produced an intensity image for the entire area using average binning in ArcGIS Pro, with no normalization or corrections applied.
• 2024-02-02 00:00:00 - The NOAA Office for Coastal Management (OCM) downloaded 1 GeoTiff data file from the Alaska Division of Geological and Geophysical Surveys (AK DGGS) for the Wrangell Island, AK project. The bare earth raster file was at a 0.5 m grid spacing. The data were in UTM Zone 8N NAD83 (2011), meters coordinates and NAVD88 (Geoid12b) elevations in meters. The single large file was retiled to 55 smaller tiles using gdal_retile.py. OCM assigned the appropriate EPSG codes (Horiz - 6337, Vert - 5703) and copied the raster files to https for Digital Coast storage and provisioning purposes.

Data is available online for bulk and custom downloads.

Data is backed up to cloud storage.