Lidar-derived elevation data for Wrangell Island, Southeast Alaska, collected July 2023

Zechmann, J.M.Wikstrom Jones, K.M.Wolken, G.J.2023Lidar-derived elevation data for Wrangell Island, Southeast Alaska, collected July 2023dataRaw Data FileRDF 2023-28 v. 1.1Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys14 p.https://doi.org/10.14509/31098Lidar-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).The survey provides snow-free surface elevations for use in shoreline development, resource quantification, hydrographic mapping, and slope stability modeling.>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 LASer (LAS) format. Data are classified following ASPRS 2019 guidelines (table 2) and contain return and intensity information. For all ground points, the average point spacing is 54.6 cm, and the average density is 3.35 pts/m2. >dsm: 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 50-cm resolution. No Data value is set to -9999. >dtm: 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 -9999. >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, 16-bit unsigned GeoTIFF file of 50-cm resolution. No Data value is set to 0.2023062620230711ground conditioncompleteNone planned-132.396167-131.92000756.49421956.115756ISO 19115 Topic CategorygeoscientificInformationAlaska Division of Geological & Geophysical SurveysAerialAerial GeologyAerial PhotographyCoastalCoastal and RiverDGGSDigital Elevation ModelDigital Surface Model (DSM)Digital Terrain ModelElevationEmergency PreparednessEngineeringEngineering GeologyEnvironmentalGeologicGeologic HazardsGeological ProcessGeologyGeomorphologyGeotechnicalHazardsHillshade ImageLiDARLiDAR Intensity ImageLiDAR LAS File FormatPoint Cloud DataRaster ImageRemote SensingSlopeSurfaceSurficialSurficial GeologyTopographyWaterAlaska Division of Geological & Geophysical SurveysBlake ChannelBradfield CanalCemetery PointChichagof PeakDewey HillDouble RockEastern PassageErnest SoundHighbush LakeInstitute CreekLong LakeMcCormack CreekNemo PointPat CreekPats LakePoint HighfieldPoint ShekestiRainbow FallsShoemaker BaySoutheast AlaskaThe NarrowsThoms CreekThoms LakeThoms PointTrout LakeTurn IslandTurn PointWrangellWrangell HarborWrangell IslandZimovia IsletsZimovia StraitThis 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.This survey area is on the traditional homelands of the Stikine Tlingit people. For this project, we partnered with the U.S. Forest Service to cost-share the acquisition of lidar data in an area of mutual interest. We thank Clearwater Air for their aviation expertise and contribution to these data products, Dustin Wittwer and Joe Delabrue of the U.S. Forest Service for logistical help, and David Ciampa and Amy Helkenn of the Alaska Division of Mining, Land and Water for providing ground control points. 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.Stevens, D.S.P.Wolken, G.J.Hubbard, T.D.Hendricks, K.A.2018Landslides in AlaskaInformation CircularIC 65Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys2 phttps://doi.org/10.14509/29849Timm, KristinWolken, G.J.2017Deglacierization and the development of glacier-related hazardsInformation CircularIC 63Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys3 phttps://doi.org/10.14509/29752Wolken, 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 applicableThis is a full-release dataset. There was no over-collect. Data quality is consistent throughout the survey.This data relaease is complete.We did not measure horizontal accuracy for this collection.We measured a mean offset of +94.3 cm between 43 control points and the point cloud. This offset was reduced to +0.9 cm in non-vegetated areas and +10.5 cm in vegetated areas by applying a rubber-sheet vertical correction to the lidar point data. We used 214 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 root mean square error (RMSE) of 5.3 cm in non-vegetated areas and 17.4 cm in vegetated areas (app. 3). We evaluated the relative accuracy for this dataset as the interswath overlap consistency and measured it at 6.4 cm RMSE.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.20230630Aerial 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.20230711Lidar 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.2023Version 1.1 update - we ran new classification macros on the pointcloud to improve building and high vegetation class code accuracy. This pointcloud and updated dtm, dsm, and intensity raster are published as version 1.1 of the Wrangell Island July 2023 data.2025rasterUniversal 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.DGGSboundariesclassified_pointsClassified point cloud data are provided in LASer (LAS) format. Data are classified following ASPRS 2019 guidelines (table 2) and contain return and intensity information. For all ground points, the average point spacing is 54.6 cm, and the average density is 3.35 pts/m2.DGGSclassified_pointsdsmThe DSM represents surface elevations, including heights of vegetation, buildings, powerlines, bridge decks, etc. The DSM is a single-band, 32-bit GeoTIFF file of 50-cm resolution. No Data value is set to -9999.DGGSdsmdtmThe 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 -9999.DGGSdtmlidar_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, 16-bit unsigned GeoTIFF file of 50-cm 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