Lidar-derived elevation data for Thane Road, Southeast Alaska, collected September 6, 2019

Wikstrom Jones, K.M.Wolken, G.J.2024Lidar-derived elevation data for Thane Road, Southeast Alaska, collected September 6, 2019dataRaw Data FileRDF 2024-16Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveyshttps://doi.org/10.14509/31278Lidar-derived elevation data for Thane Road, Southeast Alaska, collected September 6, 2019, Raw Data File 2024-16, provides aerial lidar-derived classified point cloud data, a digital surface model (DSM), a digital terrain model (DTM), and an intensity model of Mount Roberts and Gastineau Peak along Thane Road, Southeast Alaska. The survey provides snow-free surface elevations for deriving snow depth distribution models with repeat surveys during snow-covered conditions. Ground control data were collected on September 5, 2019, and aerial lidar data were collected on September 6, 2019, 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/10.14509/31278).The survey provides snow-free surface elevations for deriving snow depth distribution models with repeat surveys during snow-covered conditions.>boundaries: A boundary, also known as an Area of Interest (AOI) or border, that defines the area covered by the data. Also includes footprints for tiled data. >classified_points: Classified point cloud data are provided in LAZ format. Data are classified following ASPRS 2019 guidelines and contain return and intensity information. For classified ground points, the average point density is 4.63 pts/m2 and the average spacing is 46.5 cm. >dsm_hydro_conditioned: The DSM represents surface elevations, including heights of vegetation, buildings, powerlines, bridge decks, etc. The DSM is a single-band, 32-bit GeoTIFF file of 1-m resolution. No Data value is set to -3.40282306074e+38 (32-bit, floating-point minimum). >dtm_hydro_conditioned: The DTM represents bare earth elevations, excluding vegetation, bridge decks, buildings, etc. The DTM is a single-band, 32-bit GeoTIFF file of 50-cm resolution. No Data value is set to -3.40282306074e+38. >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. No Data value is set to 0.2019090520190906ground conditioncompleteNone planned-134.414227-134.20609358.30776758.202867ISO 19115 Topic CategorygeoscientificInformationAlaska Division of Geological & Geophysical SurveysDGGSDigital Elevation ModelDigital Surface Model (DSM)Digital Terrain ModelElevationEngineeringEngineering GeologyEnvironmentEnvironmentalGeologicGeologic HazardsGeological ProcessGeologyGeotechnicalHazardsLand SubsidenceLandslideLiDARLiDAR Intensity ImageLiDAR LAS File FormatRemote SensingSurfaceTopographyAlaska Division of Geological & Geophysical SurveysChicken RidgeCourt House HillCrooked GulchCross Bay CreekDupont CreekGastineau ChannelGastineau PeakGlacier BasinGold CreekJuneauLost Rocker FallsMount MariaPoint SalisburyRoberts PeakSheep CreekSnowslide CreekStarr HillStephens PassageSuicide FallsThaneTimber GulchThis 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

3354 College Road

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.These data products were funded by the U.S. Geological Survey, Alaska Electric Light & Power Company, and the State of Alaska and collected and processed by DGGS. We thank Coastal Helicopters for their aviation expertise and contribution to these data products. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government.Wolken, G.J.Hendricks, K.A.Daanen, R.P.Overbeck, J.R.Stevens, D.S.P.Masterman, S.S.2017Alaska & climate changeInformation CircularIC 64Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys2 phttps://doi.org/10.14509/29781Not applicableDGGS visually inspected the images for data errors such as shifts, seamline mismatches, and water noise overlapping land. Data quality is consistent throughout the survey.This is a complete release dataset. There was no over-collect except for aircraft turns that were eliminated from the dataset.Horizontal accuracy was not measured for this collection.We measured a mean offset of -5.4 cm between 24 control points and the point cloud. This offset was reduced to +4.8 cm by applying a constant vertical correction to the lidar point data. We used six checkpoints to determine the vertical accuracy of the point cloud ground class using a Triangulated Irregular Network (TIN) approach. The project vertical accuracy has a mean absolute error (MAE) of 9.1 cm. We evaluated the relative accuracy for this dataset as the interswath overlap consistency and measured a root mean square error of 10.0 cm.Ground survey - Ground control points were collected September 5, 2019. We deployed a Trimble R7 GNSS receiver with Zephyr-2 antenna at benchmark AI4980 in downtown Juneau to provide a base station occupation and real-time kinematic (RTK) corrections to points we surveyed with a rover Trimble R8-4 GNSS receiver (internal antenna). We collected 30 ground control points and checkpoints to use for calibration and to assess the vertical accuracy of the point cloud. Checkpoints were collected on bare earth (gravel or pavement).20190905Aerial survey - DGGS used a Riegl VUX1-LR 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 820,000 points per second at a range of 150 m or a minimum of 50,000 points per second at a range of 820 m (ranges assume greater than or equal to 20 percent natural reflectance). The scanner operated with a pulse refresh rate of 50,000-400,000 pulses per second and a scan rate of 80-220 revolutions per second. We used a Bell 206 Jet Ranger helicopter platform to survey from an elevation of approximately 130 m above ground level, at a ground speed of approximately 30 m/s, and with a scan angle set from 80 to 280 degrees. The total survey area covers approximately 33.7 km2. The survey area was accessed by air from the Juneau International Airport. Data collection occurred between 5:10 pm and 7:00 pm (ADT), and the weather throughout the survey was clear with no wind.20190906Lidar dataset processing - We processed point data in SDCimport software 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 17.6 pulses/m2, and the average pulse spacing is 23.8 cm. 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. Raster products were derived from the point cloud in ArcGIS Pro. A 1-m DSM was interpolated from ground, vegetation, bridge deck, and building classes using a triangulation method. A 1-m DTM was interpolated from all ground class returns, also using a triangulation method. We also produced a 1-m intensity image for the entire area using average binning, with no normalization or corrections applied. We hydro-conditioned the DTM and DSM in ArcGIS Pro by masking the shoreline and assigning any pixels located underwater an elevation of 0 m asl. This assigned elevation value does not account for tide activity, so the shoreline may appear abrupt in some areas.2023rasterUniversal Transverse Mercator80.999600-1350500000.0000000coordinate pair.00000001.00000001MetersNAD83 (2011)GRS 806378137298.257222101NAVD88, GEOID12B0.001metersExplicit 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. Also includes footprints for tiled data.DGGSboundariesclassified_pointsClassified point cloud data are provided in LAZ format. Data are classified following ASPRS 2019 guidelines and contain return and intensity information. For classified ground points, the average point density is 4.63 pts/m2 and the average spacing is 46.5 cm.DGGSclassified_pointsdsm_hydro_conditionedThe DSM represents surface elevations, including heights of vegetation, buildings, powerlines, bridge decks, etc. The DSM is a single-band, 32-bit GeoTIFF file of 1-m resolution. No Data value is set to -3.40282306074e+38 (32-bit, floating-point minimum).DGGSdsm_hydro_conditioneddtm_hydro_conditionedThe DTM represents bare earth elevations, excluding vegetation, bridge decks, buildings, etc. The DTM is a single-band, 32-bit GeoTIFF file of 50-cm resolution. No Data value is set to -3.40282306074e+38.DGGSdtm_hydro_conditionedlidar_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. No Data value is set to 0.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