2019 AK DGGS Lidar DEM: Pilgrim Hot Springs, Alaska

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Airborne survey - The airborne survey occurred on August 15, 2019. The weather was clear throughout the survey. This dataset includes point cloud data, a digital terrain model (DTM), and a digital surface model (DSM) covering Pilgrim Hot Springs, western Alaska (approximately 47 mi2). This survey was conducted with a DGGS-operated Riegl VUX1-LR lidar system with an integrated Global Navigation Satellite System (GNSS) receiver and Northrop Grumman inertial measurement unit (IMU) system. The integration was designed by Phoenix LiDAR systems. This survey was flown with a pulse rate between 200,000 and 400,000 pulses/second, at a scan rate between 80 and 150 scans/second. This survey was flown with an average elevation of 400 m above ground level and a ground speed of approximately 40 m/s with a fixed-wing aircraft configuration, using a Cessna 185 aircraft. The scan angle was set from 55 to 305 degrees, centered normal to the bottom of the aircraft.

Ground survey - Trimble R8 and R9 real-time kinematic GNSS systems were used to collect 62 combined checkpoints and control points for the project. Points were adjusted for accuracy according to Online Positioning User Service (OPUS) corrections in Trimble Business Center.

Lidar dataset processing - Point data were processed in SDCimport software for initial filtering and multiple-time-around (MTA) disambiguation. MTA errors, corrected in this process, are the result of imprecise interpretations of received pulse time intervals and occur more frequently with higher pulse refresh rates. IMU and GPS data were used to integrate flightline information with the point cloud in Spatial Explorer software. The point data were calibrated at an incrementally precise scale of sensor movement and behavior, incorporating sensor velocity, roll, pitch, and yaw fluctuations throughout the survey. Points were classified in accordance with the American Society for Photogrammetry and Remote Sensing (ASPRS) 2014 guidelines, using macros designed in Terrasolid software. Careful attention was given to the interpolation of the project's ground surface to compensate for inconsistent penetration through low vegetation as a function of the scan angle. Once classified, points underwent a geometric transformation and were converted from ellipsoidal heights to GEOID12B (Alaska) heights. Raster products were derived from the point cloud using ArcMap. The DTM was interpolated from all ground class returns using a mean binning method. The DSM was likewise interpolated from only the first returns for all classes. An intensity image was produced in ArcMap using mean binning.

Data were retrieved from the Alaska DGGS elevation portal then reorganized into cloud optimized geotiff format and ingested into the Data Access Viewer system.