Identification_Information: Citation: Citation_Information: Originator: Zechmann, J.M. Originator: Larsen, M.C. Originator: Wolken, G.J. Publication_Date: 2024 Title: Lidar-derived elevation data for Ketchikan, Southeast Alaska, collected August 29, 2024 Geospatial_Data_Presentation_Form: data Series_Information: Series_Name: Raw Data File Issue_Identification: RDF 2024-31 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Other_Citation_Details: 14 p Online_Linkage: https://doi.org/10.14509/31453 Description: Abstract: 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). Purpose: 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. Supplemental_Information: >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. Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 20240825 Ending_Date: 20240829 Currentness_Reference: ground condition Status: Progress: complete Maintenance_and_Update_Frequency: None planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -131.709101 East_Bounding_Coordinate: -131.632633 North_Bounding_Coordinate: 55.375221 South_Bounding_Coordinate: 55.336633 Keywords: Theme: Theme_Keyword_Thesaurus: ISO 19115 Topic Category Theme_Keyword: geoscientificInformation Theme: Theme_Keyword_Thesaurus: Alaska Division of Geological & Geophysical Surveys Theme_Keyword: Aerial Theme_Keyword: Coastal Theme_Keyword: Coastal and River Theme_Keyword: Coastal and River Hazards Theme_Keyword: DGGS Theme_Keyword: Debris Flow Theme_Keyword: Digital Elevation Model Theme_Keyword: Digital Surface Model (DSM) Theme_Keyword: Digital Terrain Model Theme_Keyword: Elevation Theme_Keyword: Emergency Preparedness Theme_Keyword: Engineering Theme_Keyword: Engineering Geology Theme_Keyword: Environmental Theme_Keyword: Geologic Theme_Keyword: Geologic Hazards Theme_Keyword: Geological Process Theme_Keyword: Geology Theme_Keyword: Geomorphology Theme_Keyword: Geotechnical Theme_Keyword: Hazards Theme_Keyword: Landslide Theme_Keyword: Landslide Deposit Theme_Keyword: Landslide Susceptibility Theme_Keyword: LiDAR Theme_Keyword: LiDAR Intensity Image Theme_Keyword: LiDAR LAS File Format Theme_Keyword: Point Cloud Data Theme_Keyword: Raster Image Theme_Keyword: Remote Sensing Theme_Keyword: Rock Avalanche Theme_Keyword: Rockfall Theme_Keyword: Slope Theme_Keyword: Slope Instability Theme_Keyword: Slope Instability Hazards Theme_Keyword: Surface Theme_Keyword: Surficial Theme_Keyword: Surficial Geology Theme_Keyword: Topography Place: Place_Keyword_Thesaurus: Alaska Division of Geological & Geophysical Surveys Place_Keyword: Bar Point Place_Keyword: Carlanna Creek Place_Keyword: Carlanna Lake Place_Keyword: Charcoal Point Place_Keyword: City of Ketchikan Place_Keyword: Hoadley Creek Place_Keyword: Ketchikan Place_Keyword: Ketchikan Creek Place_Keyword: Ketchikan Harbor Place_Keyword: Level Mountain 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). 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. Point_of_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: Alaska Division of Geological & Geophysical Surveys Contact_Position: GIS Manager Contact_Address: Address_Type: mailing and physical Address: 3354 College Rd City: Fairbanks State_or_Province: AK Postal_Code: 99709-3707 Country: USA Contact_Voice_Telephone: 907-451-5020 Contact_Electronic_Mail_Address: dggsgis@alaska.gov Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays Data_Set_Credit: 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. Cross_Reference: Citation_Information: Originator: Stevens, D.S.P. Originator: Wolken, G.J. Originator: Hubbard, T.D. Originator: Hendricks, K.A. Publication_Date: 2018 Title: Landslides in Alaska Series_Information: Series_Name: Information Circular Issue_Identification: IC 65 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Other_Citation_Details: 2 p Online_Linkage: https://doi.org/10.14509/29849 Cross_Reference: Citation_Information: Originator: Suleimani, E.N. Originator: Salisbury, J.B. Originator: Nicolsky, D.J. Originator: Koehler, R.D. Publication_Date: 2019 Title: Regional tsunami hazard assessment for the communities of Port Alexander, Craig, and Ketchikan, southeast Alaska Series_Information: Series_Name: Report of Investigation Issue_Identification: RI 2019-7 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Other_Citation_Details: 23 p., 5 sheets Online_Linkage: https://doi.org/10.14509/30196 Cross_Reference: Citation_Information: Originator: Wolken, G.J. Originator: Hendricks, K.A. Originator: Daanen, R.P. Originator: Overbeck, J.R. Originator: Stevens, D.S.P. Originator: Masterman, S.S. Publication_Date: 2017 Title: Alaska & climate change Series_Information: Series_Name: Information Circular Issue_Identification: IC 64 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Other_Citation_Details: 2 p Online_Linkage: https://doi.org/10.14509/29781 Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: Not applicable Logical_Consistency_Report: 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. Completeness_Report: This is a full-release dataset. Positional_Accuracy: Horizontal_Positional_Accuracy: 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: 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. Lineage: Process_Step: Process_Description: 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. Process_Date: 20240825 Process_Step: Process_Description: 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. Process_Date: 20240831 Process_Step: Process_Description: 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. Process_Date: 202411 Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: raster Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Grid_Coordinate_System: Grid_Coordinate_System_Name: Universal Transverse Mercator Universal_Transverse_Mercator: UTM_Zone_Number: 9 Transverse_Mercator: Scale_Factor_at_Central_Meridian: 0.999600 Longitude_of_Central_Meridian: -129 Latitude_of_Projection_Origin: 0 False_Easting: 500000.000000 False_Northing: 0 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: coordinate pair Coordinate_Representation: Abscissa_Resolution: .00000001 Ordinate_Resolution: .00000001 Planar_Distance_Units: Meters Geodetic_Model: Horizontal_Datum_Name: NAD83 (2011) Ellipsoid_Name: GRS 80 Semi-major_Axis: 6378137 Denominator_of_Flattening_Ratio: 298.257222101 Vertical_Coordinate_System_Definition: Altitude_System_Definition: Altitude_Datum_Name: NAVD88, GEOID12B Altitude_Resolution: 0.500000 Altitude_Distance_Units: meters Altitude_Encoding_Method: Explicit elevation coordinate included with horizontal coordinates Entity_and_Attribute_Information: Detailed_Description: Entity_Type: Entity_Type_Label: boundaries Entity_Type_Definition: 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. Entity_Type_Definition_Source: DGGS Entity_Attribute_Layer_Name: boundaries Detailed_Description: Entity_Type: Entity_Type_Label: classified_points Entity_Type_Definition: 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. Entity_Type_Definition_Source: DGGS Entity_Attribute_Layer_Name: classified_points Detailed_Description: Entity_Type: Entity_Type_Label: dsm Entity_Type_Definition: 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. Entity_Type_Definition_Source: DGGS Entity_Attribute_Layer_Name: dsm Detailed_Description: Entity_Type: Entity_Type_Label: dtm Entity_Type_Definition: 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. Entity_Type_Definition_Source: DGGS Entity_Attribute_Layer_Name: dtm Detailed_Description: Entity_Type: Entity_Type_Label: lidar_intensity Entity_Type_Definition: 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. Entity_Type_Definition_Source: DGGS Entity_Attribute_Layer_Name: lidar_intensity Distribution_Information: Distributor: Contact_Information: Contact_Organization_Primary: Contact_Organization: State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys Contact_Person: Simone Montayne Contact_Address: Address_Type: mailing and physical Address: 3354 College Road City: Fairbanks State_or_Province: AK Postal_Code: 99709-3707 Country: USA Contact_Voice_Telephone: 907-451-5020 Contact_Facsimile_Telephone: 907-451-5050 Contact_Electronic_Mail_Address: dggspubs@alaska.gov Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays Contact_Instructions: 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. Resource_Description: RDF 2024-31 Distribution_Liability: 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. Standard_Order_Process: Non-digital_Form: DGGS publications are available as free online downloads. You may purchase paper hard-copies or digital files on CD/DVD or other digital storage media by mail, phone, fax, or email from the DGGS Fairbanks office. To purchase this or other printed reports and maps, contact DGGS by phone (907-451-5020), e-mail (dggspubs@alaska.gov), or fax (907-451-5050). Payment accepted: Cash, check, money order, VISA, or MasterCard. Turnaround time is 1-2 weeks unless special arrangements are made and an express fee is paid. Shipping charge will be the actual cost of postage and will be added to the total amount due. Contact us for the exact shipping amount. Fees: see http://dx.doi.org/10.14509/31453 Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: data Format_Version_Date: 20241209 Format_Information_Content: boundaries, classified points, dsm, dtm and lidar intensity Digital_Transfer_Option: Online_Option: Computer_Contact_Information: Network_Address: Network_Resource_Name: http://dx.doi.org/10.14509/31453 Fees: Free download Metadata_Reference_Information: Metadata_Date: 20241209 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Simone Montayne Contact_Address: Address_Type: mailing and physical Address: 3354 College Road City: Fairbanks State_or_Province: AK Postal_Code: 99709-3707 Country: USA Contact_Voice_Telephone: 907-451-5020 Metadata_Standard_Name: FGDC Content Standard for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998 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. Metadata_Extensions: Online_Linkage: http://www.dggs.alaska.gov/metadata/dggs.ext Profile_Name: dggs metadata extensions