484afa76-2bdd-4d63-8f9f-0b22d48e5061_source eng; USA utf8 dataset Simone Montayne 907-451-5020 3354 College Road Fairbanks AK 99709-3707 USA pointOfContact 2024-12-09 ISO 19115 Geographic Information - Metadata ISO 19115:2003/Cor.1:2006(E) Lidar-derived elevation data for Ketchikan, Southeast Alaska, collected August 29, 2024 2024-01-01 publication Alaska Division of Geological & Geophysical Surveys Fairbanks Alaska, United States publisher Zechmann, J.M. originator Larsen, M.C. originator Wolken, G.J. originator https://doi.org/10.14509/31453 DATA Raw Data File RDF 2024-31 14 p Lidar-derived elevation data for Ketchikan, Southeast Alaska, collected August 29, 2024, Raw Data File 2024-31, releases classified point cloud derived from aerial lidar, along with a digital surface model (DSM), a digital terrain model (DTM), and an intensity model of Ketchikan, Southeast Alaska. The data were collected during leaf-on conditions and provides snow-free surface elevations useful for landslide hazard analysis. The Division of Geological and Geophysical Surveys (DGGS) conducted the lidar survey following a fatal landslide in downtown Ketchikan on August 25, 2024. The lidar flight took place on August 29, 2024, with ground control values acquired on August 30 and 31, 2024. The staff then merged and processed the data using geospatial processing software. This collection is available as a Raw Data File under an open end-user license. All files can be downloaded from the Alaska Division of Geological & Geophysical Surveys website (http://doi.org/10.14509/31453). The data were collected during leaf-on conditions and provides snow-free surface elevations useful for landslide hazard analysis. The Division of Geological and Geophysical Surveys (DGGS) conducted the lidar survey following a fatal landslide in downtown Ketchikan on August 25, 2024. This survey area lies within the traditional homelands of the Tlingit peoples. This work was funded by the Alaska Department of Military and Veterans Affairs Division of Homeland Security and Emergency Management through emergency response funds from the Federal Emergency Management Agency. We thank Coastal Helicopters for their expertise and contribution to these data products and Temsco Helicopters for allowing us to use their facilities. We also thank the residents, first responders, and road clearing workers of Ketchikan for allowing us to operate in the landslide area. 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 State of Alaska. completed Alaska Division of Geological & Geophysical Surveys GIS Manager 907-451-5020 3354 College Rd Fairbanks AK 99709-3707 USA dggsgis@alaska.gov 8 am to 4:30 pm, Monday through Friday, except State holidays pointOfContact notPlanned Aerial Coastal Coastal and River Coastal and River Hazards DGGS Debris Flow Digital Elevation Model Digital Surface Model (DSM) Digital Terrain Model Elevation Emergency Preparedness Engineering Engineering Geology Environmental Geologic Geologic Hazards Geological Process Geology Geomorphology Geotechnical Hazards Landslide Landslide Deposit Landslide Susceptibility LiDAR LiDAR Intensity Image LiDAR LAS File Format Point Cloud Data Raster Image Remote Sensing Rock Avalanche Rockfall Slope Slope Instability Slope Instability Hazards Surface Surficial Surficial Geology Topography theme Alaska Division of Geological & Geophysical Surveys Bar Point Carlanna Creek Carlanna Lake Charcoal Point City of Ketchikan Hoadley Creek Ketchikan Ketchikan Creek Ketchikan Harbor Level Mountain place Alaska Division of Geological & Geophysical Surveys The State of Alaska makes no express or implied warranties (including warranties of merchantability and fitness) with respect to the character, function, or capabilities of the electronic services 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, any failure thereof, or otherwise, and 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. otherRestrictions Use Constraints: 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. otherRestrictions Access Constraints: This 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). Landslides in Alaska 2018-01-01 publication Alaska Division of Geological & Geophysical Surveys Fairbanks Alaska, United States publisher Stevens, D.S.P. originator Wolken, G.J. originator Hubbard, T.D. originator Hendricks, K.A. originator https://doi.org/10.14509/29849 Information Circular IC 65 2 p crossReference Regional tsunami hazard assessment for the communities of Port Alexander, Craig, and Ketchikan, southeast Alaska 2019-01-01 publication Alaska Division of Geological & Geophysical Surveys Fairbanks Alaska, United States publisher Suleimani, E.N. originator Salisbury, J.B. originator Nicolsky, D.J. originator Koehler, R.D. originator https://doi.org/10.14509/30196 Report of Investigation RI 2019-7 23 p., 5 sheets crossReference Alaska & climate change 2017-01-01 publication Alaska Division of Geological & Geophysical Surveys Fairbanks Alaska, United States publisher Wolken, G.J. originator Hendricks, K.A. originator Daanen, R.P. originator Overbeck, J.R. originator Stevens, D.S.P. originator Masterman, S.S. originator https://doi.org/10.14509/29781 Information Circular IC 64 2 p crossReference grid eng; USA geoscientificInformation -131.709101 -131.632633 55.336633 55.375221 2024-08-25 2024-08-29 >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 12.4 pts/m2 and the average spacing is 28.4 cm; within the high-priority region, the average ground point density is 11.5 pts/m2 and the average spacing is 29.4 cm. >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 -3.40282306074e+38 (32-bit, floating-point minimum). The DSM from the high-priority area is a single-band, 32-bit GeoTIFF file of 20-cm resolution, with a No Data value of -3.40282306074e+38. >dtm: The DTM represents bare earth or snow surface 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. The DTM from the high-priority area is a single-band, 32-bit GeoTIFF file of 20-cm resolution, with a No Data value of -3.40282306074e+38. >lidar_intensity: The lidar intensity image illustrates 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 20-cm resolution. No Data value is set to 0. true data unknown Simone Montayne State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys 907-451-5020 907-451-5050 3354 College Road Fairbanks AK 99709-3707 USA dggspubs@alaska.gov 8 am to 4:30 pm, Monday through Friday, except State holidays Please view our website (http://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible. distributor see http://dx.doi.org/10.14509/31453 Free download http://dx.doi.org/10.14509/31453 data boundaries, classified points, dsm, dtm and lidar intensity information dataset Horizontal Positional Accuracy Report The offset between the intensity image and 25 ground control points was -115.6 cm measured west to east and +57.9 cm measured south to north. This was reduced to +0.7 cm and +4.4 cm, respectively, by applying a constant horizontal correction. We used 26 checkpoints to determine the horizontal accuracy of the corrected point cloud by measuring the offset between checkpoints and their respective locations in an intensity image produced from the corrected point cloud. The project horizontal accuracy has a root mean square error (RMSE) of 7.6 cm in the east-west direction and 15.9 cm in the north-south direction. Vertical Positional Accuracy Report We measured a mean elevation offset of -10.2 cm between 58 control points and the horizontally corrected point cloud. This offset was reduced to -0.1 cm by applying a constant vertical correction to the lidar point data. We used 57 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 6.4 cm. We evaluated the relative accuracy for this dataset as the interswath overlap consistency and measured it at 7.6 cm RMSE. This is a full-release dataset. This is a full-release dataset. DGGS visually inspected the orthoimage for data errors such as shifts, seamline mismatches, and water noise overlapping land. Visual errors common to these SfM photogrammetry products include discontinuous powerlines and distortion near high-angle features like buildings, as well as water boundaries. Highly reflective objects such as water bodies, metal roofs, and white paint may cause overexposure, leading to spurious elevation points. There were no significantly erroneous areas that required repair. This lineage was generated by the FGDC CSDGM to 19139 transformation Aerial 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 greater than or equal to 20 percent natural reflectance). The scanner operated with a pulse refresh rate of 800,000 pulses per second at a scan rate of 160 revolutions per second. We used a Bell 206 helicopter to survey from an elevation of approximately 100-300 m above ground level, at a ground speed of roughly 30 m/s, and with a scan angle set from 80 to 280 degrees. The total survey area covers approximately 11.1 km2, with a 3.1 km2 portion of the block considered a priority area of interest (blue outline in the cover figure). The survey area was accessed by air from Temsco Helicopters in Ketchikan. Data were collected from 12:05 pm to 1:05 pm and from 3:05 pm to 4:00 pm (AKST). The weather throughout the survey was overcast with scattered low-level clouds and no wind. For a GNSS base station occupation to later correct lidar survey flightlines, we set up a Trimble R10-2 on a jetty on Tongass Narrows. 2024-08-25T00:00:00 Ground survey - Ground control points were collected from August 30-31, 2024. We deployed a Trimble R10-2 GNSS base receiver on a jetty along Tongass Narrows and surveyed points with a rover Trimble R10-2 GNSS receiver/Mesa controller within the survey area. We collected 115 ground control points and checkpoints, with 51 located on markers (crosswalks and other paint lines) with enough intensity contrast with their surroundings that they were visible in the lidar data. Surveyed points were used to correct the point cloud vertically and horizontally and to calculate the vertical and horizontal accuracy of the corrected point cloud. The checkpoints and ground control points were collected on bare earth (i.e., gravel, dirt, or pavement). We processed and delivered all data in NAD83 (2011) UTM9N and vertical datum NAVD88 GEOID12B. 2024-08-31T00:00:00 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. 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 218.7 pulses/m2, and the average pulse spacing is 6.8 cm. Within the priority region, the average pulse density is 325.4 pulses/m2, and the average pulse spacing is 5.6 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 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 50-cm DSM was interpolated from maximum elevations of the ground, vegetation, bridge deck, wire, and building classes using a binning method. A 50-cm DTM was interpolated from all ground-class returns using a binning method and minimum elevation values. We also produced a 20-cm intensity image using average binning in ArcGIS Pro, with no normalization or corrections applied. Higher-resolution elevation products were also produced within the high-priority region. A 20-cm DSM was interpolated from elevation values in the ground, vegetation, bridge deck, wire, and building classes using a triangulation method. A 20-cm DTM was made using a triangulation interpolation from all ground-class returns. 2024-11-01T00:00:00 otherRestrictions Metadata Use Constraints: If the user has modified this metadata file in any way, the user is obligated to describe the types of modifications the user has made. User specifically agrees not to misrepresent this metadata file, 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. unknown This metadata was automatically generated from the FGDC Content Standard for Digital Geospatial Metadata standard (version FGDC-STD-001-1998) using the 2019-08-12T11:11:00 version of the FGDC CSDGM to ISO 19139 transform. Simone Montayne 907-451-5020 3354 College Road Fairbanks AK 99709-3707 USA pointOfContact