Lidar-derived surface elevation data for Glen Alps, Southcentral Alaska, collected August 17, 2024

Wikstrom Jones, KatreenWolken, G.J.2025Lidar-derived surface elevation data for Glen Alps, Southcentral Alaska, collected August 17, 2024dataRaw Data FileRDF 2025-19Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys8 p.https://doi.org/10.14509/31704Lidar-derived surface elevation data for Glen Alps, Southcentral Alaska, collected August 17, 2024, Raw Data File 2025-19, releases classified point cloud, digital surface model (DSM), digital terrain model (DTM), and intensity model of the Glen Alps area, Municipality of Anchorage (MOA), Southcentral Alaska, during leaf-on conditions. The survey provides summer 'snow off' surface elevations to derive snow depth information using a separately collected winter 'snow-on' elevation surface. Ground control data were collected on March 25, 2024, and aerial lidar data were collected on August 17, 2024, and subsequently merged and processed using a suite of geospatial processing software. This data collection is released as a Raw Data File with an open end-user license. All files can be downloaded from the Alaska Division of Geological & Geophysical Surveys website (http://doi.org/10.14509/31704).The data was released to support accurate snow depth analysis and surface elevation modeling in the Glen Alps area by providing high-resolution lidar datasets collected during leaf-on and snow-off conditions.>boundaries: A boundary, also known as an Area of Interest (AOI) or border, that defines the area covered by the data. >classified_points: Classified point cloud data are provided in LAZ format. Data are classified following ASPRS 2019 guidelines (table 1) and contain return and intensity information. For classified ground points, the average point density is 10.2 pts/m2, and the average spacing is 31.2 cm. >dsm: The DSM represents surface elevations, including vegetation heights, buildings, and power lines. It is a single-band, 32-bit GeoTIFF file with a 1-m resolution and a No Data value set to -3.40282306074e+38 (32-bit, floating-point minimum). >dtm: The DTM represents bare earth or snow surface elevations, excluding vegetation and built structures. It is a single-band, 32-bit GeoTIFF file with a 1-m resolution and a No Data value set to -3.40282306074e+38. >footprints: Footprints for tiled data. >lidar_intensity: The lidar intensity image describes the relative amplitude of reflected signals contributing to the point cloud. Lidar intensity is (1) primarily a function of scanned object reflectance in relation to the signal frequency, (2) dependent on ambient conditions, and (3) not necessarily consistent between separate scans. The intensity image is a single-band, 32-bit GeoTIFF file of 1-m resolution, with a No Data value set to -3.40282306074e+38.2024032520240817ground conditioncompleteNone planned-149.731247-149.60028261.12078261.046644ISO 19115 Topic CategorygeoscientificInformationAlaska Division of Geological & Geophysical SurveysAerialAerial GeologyAvalancheCoastalCoastal and RiverDGGSDigital Elevation ModelDigital Surface Model (DSM)Digital Terrain ModelElevationEmergency PreparednessEngineeringEngineering GeologyEnvironmentalGeologicGeologic HazardsGeological ProcessGeologyGeomorphologyGeotechnicalLiDARLiDAR Intensity ImageLiDAR LAS File FormatPoint Cloud DataRaster ImageRemote SensingSlopeSlope InstabilitySnow AvalancheSurfaceTopographyAlaska Division of Geological & Geophysical SurveysAnchorage Mining DistrictFlattop MountainRabbit CreekThis report, map, and/or dataset is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below).Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. The user specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.Alaska Division of Geological & Geophysical SurveysMetadata Managermailing and physical

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FairbanksAK99709-3707USA(907)451-5020(907)451-5050dggspubs@alaska.gov8 am to 4:30 pm, Monday through Friday, except State holidaysPlease view our website (https://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible.This work was funded by the Federal Emergency Management Agency for the Municipality of Anchorage Grant # EMS-2023-CA-05010. We thank Clearwater Air for their expertise and contribution to these data products.Wikstrom Jones, K.M.Wolken, G.J.Daanen, R.P.Herbst, A.M.2021Lidar-derived elevation data for Turnagain Pass, southcentral Alaska, September 2, 2018Raw Data FileRDF 2020-16Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys7 phttps://doi.org/10.14509/30567Wikstrom Jones, K.M.Wolken, G.J.2024Lidar-derived elevation data for Penguin Ridge, southcentral Alaska, collected September 22, 2021Raw Data FileRDF 2024-5Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys11 phttps://doi.org/10.14509/31158Wikstrom Jones, K.M.Wolken, G.J.2024Lidar-derived elevation data for Thane Road, southeast Alaska, collected September 6, 2019Raw Data FileRDF 2024-16Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys7 phttps://doi.org/10.14509/31278Zechmann, J.M.Wikstrom Jones, K.M.Wolken, G.J.2024Lidar-derived elevation data for Portage, southcentral Alaska, collected October 15, 2020Raw Data FileRDF 2024-7Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys10 phttps://doi.org/10.14509/31160Not applicableData quality is consistent throughout the survey, save for gaps over snow areas or in very thick vegetation between flightlines.This is a full-release dataset. There was no over-collect.Horizontal accuracy was not measured for this collection; it is considered inherent in the airborne GPS/IMU solution.The entire MOA dataset was processed as a single unit, and relative accuracy was evaluated based on interswath overlap consistency, yielding an RMSE of 2.2 cm. We measured a mean elevation offset of +68.7 cm between 30 control points and the point cloud. This offset was reduced by applying a constant vertical correction of -68.7 cm to the point cloud. A total of 30 independent non-vegetated checkpoints were evaluated, demonstrating an RMSE of 12.6 cm and yielding an NVA of 24.7 cm at the 95% confidence level. A total of 30 vegetated checkpoints were evaluated. The VVA, represented as the 95th-percentile absolute vertical error, was calculated as 92.1 cm. The dataset meets the USGS LiDAR Base Specification accuracy requirements for QL3 in all evaluated categories.Ground survey - Ground control points were collected on March 25, 2024. A Trimble R10-2 GNSS base receiver was deployed near the Glen Alps/Flattop Trailhead parking lot, with coordinates of 61 degrees, 6 minutes, 14.02880 seconds North and 149 degrees, 41 minutes, 7.75673 seconds West, at 676.3 meters elevation, and surveyed points were collected using a rover Trimble R10-2 GNSS receiver and Mesa controller within the survey area. A total of 72 ground control points and checkpoints were collected on paved surfaces. To occupy a GNSS base station and later correct lidar survey flightlines, a Trimble R10-2 was set up near the same location, collecting data at a rate of 5 Hz from 8:18 a.m. to 8:46 p.m. (AKDT) on August 17, 2024.20240325Aerial survey - DGGS used a Riegl VUX1-LR22 laser scanner with a global navigation satellite system (GNSS) and Northrop Grumman LN-200C inertial measurement unit (IMU) integrated by Phoenix LiDAR Systems. The sensor can collect a maximum of 1,500,000 points per second at a range of 230 m or a minimum of 50,000 points per second at 1,000 m (ranges assume â¥ 20 percent natural reflectance). The scanner operated with a pulse refresh rate of 400,000 pulses per second over heavily vegetated areas or a pulse refresh rate of 200,000 pulses per second over alpine areas. We used a Cessna 180 Skywagon fixed-wing platform to survey from an elevation of approximately 100-300 m above ground level, at a ground speed of approximately 40 m/s, and with a scan angle set from 80 to 280 degrees. A scan rate of 10 revolutions per second was unintentionally used for the entire survey, resulting in larger-than-expected gaps between scan lines. The total survey area covers approximately 25.7 km2. The survey area was accessed by air from Merrill Field Airport, Anchorage, and was part of a larger survey that covered additional areas of interest within the MOA. This part of the survey started at 2:26 pm AKDT and ended at 4:02 pm AKDT. The weather during the survey was partly cloudy with no-to-light wind increasing throughout the day.20240817Dataset 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. IMU and GNSS data were processed 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. For the lidar data collection, the average pulse density is 21.4 pulses/m2, and the average pulse spacing is 21.6 cm. We created a macro (an ordered list of point classification commands tailored to this dataset) 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. Raster products were derived from the point cloud in ArcGIS Pro. A 1-m DSM was interpolated from ground, vegetation, buildings, and powerline classes using a triangulation method with a 1-m resolution point thinning window, selecting maximum values. A 1-m DTM was interpolated from all ground-class returns using a triangulation method with a 5-m resolution point thinning window, selecting average values. We also produced a 1-m intensity image using average binning in ArcGIS Pro, with no normalizations or corrections.2025rasterUniversal Transverse Mercator60.999600-1470500000.0000000coordinate pair.00000001.00000001MetersNAD83 (2011)GRS 806378137298.257222101NAVD88, GEOID12B0.500000metersExplicit elevation coordinate included with horizontal coordinatesboundariesA boundary, also known as an Area of Interest (AOI) or border, that defines the area covered by the data.DGGSboundariesclassified_pointsClassified point cloud data are provided in LAZ format. Data are classified following ASPRS 2019 guidelines (table 1) and contain return and intensity information. For classified ground points, the average point density is 10.2 pts/m2, and the average spacing is 31.2 cm.DGGSclassified_pointsdsmThe DSM represents surface elevations, including vegetation heights, buildings, and power lines. It is a single-band, 32-bit GeoTIFF file with a 1-m resolution and a No Data value set to -3.40282306074e+38 (32-bit, floating-point minimum).DGGSdsmdtmThe DTM represents bare earth or snow surface elevations, excluding vegetation and built structures. It is a single-band, 32-bit GeoTIFF file with a 1-m resolution and a No Data value set to -3.40282306074e+38.DGGSdtmfootprintsFootprints for tiled data.DGGSfootprintslidar_intensityThe lidar intensity image describes the relative amplitude of reflected signals contributing to the point cloud. Lidar intensity is (1) primarily a function of scanned object reflectance in relation to the signal frequency, (2) dependent on ambient conditions, and (3) not necessarily consistent between separate scans. The intensity image is a single-band, 32-bit GeoTIFF file of 1-m resolution, with a No Data value set to -3.40282306074e+38.DGGSlidar_intensityAlaska Division of Geological & Geophysical SurveysMetadata Managermailing and physical

3354 College Road

FairbanksAK99709-3707USA(907)451-5020(907)451-5050dggspubs@alaska.gov8 am to 4:30 pm, Monday through Friday, except State holidaysFGDC Content Standard for Digital Geospatial MetadataFGDC-STD-001-1998If the user has modified the data in any way they are obligated to describe the types of modifications they have performed in the supporting metadata file. User specifically agrees not to imply that changes they made were approved by the Alaska Department of Natural Resources or Division of Geological & Geophysical Surveys.https://dggs.alaska.gov/metadata/dggs.extdggs metadata extensions