Lidar-derived elevation data for Barry Arm landslide, southcentral Alaska, October 16, 2020

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Frequently anticipated questions:


What does this data set describe?

Title:
Lidar-derived elevation data for Barry Arm landslide, southcentral Alaska, October 16, 2020
Abstract:
Lidar-derived elevation data for Barry Arm landslide, southcentral Alaska, October 16, 2020, Raw Data File 2026-5, provides classified point cloud, a digital terrain model (DTM), a surface model (DSM), and an intensity model for the Barry Arm landslide, northeast of Whittier in Prince William Sound in southcentral Alaska, during near-snow-free ground conditions. The goal of the survey is to provide snow-free surface elevation data to assess landslide movement using repeat surveys during snow-free conditions. Airborne data were collected on October 16, 2020, and subsequently processed in Terrasolid and ArcGIS. Ground control was also collected on October 16, 2020. These data are provided as a Raw Data File under an open end-user license and are available on the DGGS website (http://doi.org/10.14509/31970).
Supplemental_Information:
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. Classification follows ASPRS 2025 standards with return and intensity values. Ground-classified points have a mean density of 41.1 pts/m2 and an average spacing of 15.6 cm.	
dsm:    The DSM represents surface elevations, including heights of vegetation and structures. The DSM is a single-band, 32-bit tiled GeoTIFF dataset of 10-cm resolution. No Data value is set to -3.40282306074e+38 (32-bit, floating-point minimum).	
dtm:    The DTM represents bare earth elevations, excluding vegetation and structures. The DTM is a single-band, 32-bit tiled GeoTIFF dataset of 10-cm resolution. No Data value is 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.
  1. How might this data set be cited?
    Wikstrom Jones, K.M., Wolken, G.J., and Daanen, R.P., 2026, Lidar-derived elevation data for Barry Arm landslide, southcentral Alaska, October 16, 2020: Raw Data File RDF 2026-5, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 9 p.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -148.183029
    East_Bounding_Coordinate: -148.099108
    North_Bounding_Coordinate: 61.187321
    South_Bounding_Coordinate: 61.121755
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 16-Oct-2020
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a raster data set.
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 6
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -147
      Latitude_of_Projection_Origin: 0
      False_Easting: 500000.000000
      False_Northing: 0
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest .00000001
      Ordinates (y-coordinates) are specified to the nearest .00000001
      Planar coordinates are specified in Meters
      The horizontal datum used is NAD83 (2011).
      The ellipsoid used is GRS 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257222101.
      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
  7. How does the data set describe geographic features?
    boundaries
    A boundary, also known as an Area of Interest (AOI) or border, that defines the area covered by the data. (Source: DGGS)
    classified_points
    Classified point cloud data are provided in LAZ format. Classification follows ASPRS 2025 standards with return and intensity values. Ground-classified points have a mean density of 41.1 pts/m2 and an average spacing of 15.6 cm. (Source: DGGS)
    dsm
    The DSM represents surface elevations, including heights of vegetation and structures. The DSM is a single-band, 32-bit tiled GeoTIFF dataset of 10-cm resolution. No Data value is set to -3.40282306074e+38 (32-bit, floating-point minimum). (Source: DGGS)
    dtm
    The DTM represents bare earth elevations, excluding vegetation and structures. The DTM is a single-band, 32-bit tiled GeoTIFF dataset of 10-cm resolution. No Data value is set to -3.40282306074e+38. (Source: DGGS)
    footprints
    Footprints for tiled data. (Source: DGGS)
    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. (Source: DGGS)

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
  2. Who also contributed to the data set?
    These data products were funded by the State of Alaska Landslide Hazard Capital Improvement Project and collected and processed by DGGS. We thank Clearwater Air and Alpine Air for their aviation expertise and contribution to these data products.
  3. To whom should users address questions about the data?
    Alaska Division of Geological & Geophysical Surveys
    Metadata Manager
    3354 College Road
    Fairbanks, AK
    USA

    (907)451-5020 (voice)
    (907)451-5050 (FAX)
    dggspubs@alaska.gov
    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
    Contact_Instructions:
    Please 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.

Why was the data set created?

These elevation data products were generated to support assessment of landslide movement at the Barry Arm site. Accurate, snow‑free elevation measurements allow scientists to detect subtle changes in the terrain over time. Monitoring these changes helps identify accelerating movement, evaluate potential slope instability, and improve understanding of the landslide's behavior. This information is essential for assessing hazards, informing risk‑mitigation efforts, and supporting decision‑making for communities and infrastructure that could be affected by rapid slope failure or tsunami generation in Barry Arm.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 16-Oct-2020 (process 1 of 3)
    Ground survey - Ground control and checkpoints were collected on October 16, 2020. A Trimble R10-2 GNSS receiver with an internal antenna was deployed near the center of the study area on the ridge. It provided a base station occupation and real-time kinematic (RTK) corrections to points surveyed with a rover Trimble R10-2 GNSS receiver (internal antenna). We collected 70 ground control and check points to use for calibration and to assess the vertical accuracy of the point cloud; 67 of these were used for this lidar acquisition. Checkpoints were collected on bare earth or minimally vegetated surface.
    Date: 16-Oct-2020 (process 2 of 3)
    Aerial survey - DGGS used a Riegl VUX1-LR laser scanner with a global navigation satellite system (GNSS) and a Northrop Grumman LN-200C inertial measurement unit (IMU) integrated by Phoenix LiDAR Systems. The sensor can collect a maximum of 820,000 points per second at a range of 215 m, or a minimum of 50,000 points per second at 820 m (ranges assume greater than or equal to 20 percent natural reflectance). This survey was flown with a pulse refresh rate of 200,000 to 400,000 pulses per second and a scan rate of 80 to 150 lines per second. 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. The total area surveyed was approximately 12.6 km2. The airborne survey was flown on October 16, 2020, beginning at 9:35 am AKST and ending at 10:48 am AKST. The weather throughout the survey was fair and cloudless.
    Date: 2025 (process 3 of 3)
    Dataset processing - We processed point data in SDCimport 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 pulse density is 41.3 pulses/m2, and the average pulse spacing is 15.6 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) 2025 guidelines (ASPRS, 2025). After classification, we applied a geometric transformation to convert points from ellipsoidal heights to GEOID12B (Alaska) orthometric heights. Raster products were derived from the point cloud in ArcGIS Pro. A 20-cm DSM was interpolated from ground and vegetation classes using a triangulation method and maximum values. A 20-cm DTM was interpolated from all ground-class returns using triangulation method and minimum values. We also produced a 1-m intensity image for the area using average binning in ArcGIS Pro, with no normalization or corrections applied.
  3. What similar or related data should the user be aware of?
    Daanen, R.P., Wolken, G.J., Wikstrom Jones, K.M., and Herbst, A.M., 2021, High resolution lidar-derived elevation data for Barry Arm landslide, southcentral Alaska, June 26, 2020: Raw Data File RDF 2021-3, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 9 p
    Daanen, R.P., Wolken, G.J., Wikstrom Jones, K.M., and Herbst, A.M., 2021, Lidar-derived elevation data for upper Barry Arm, southcentral Alaska, June 26, 2020: Raw Data File RDF 2021-1, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 9 p
    Wikstrom Jones, K.M., Wolken, G.J., Daanen, R.P., and Herbst, A.M., 2021, Photogrammetry-derived orthoimagery and elevation data for Barry Arm landslide, southcentral Alaska, June 27, 2020: Raw Data File RDF 2021-5, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 6 p
    Zechmann, J.M., Wolken, G.J., and Wikstrom Jones, K.M., 2025, Lidar-derived elevation data for Barry Arm, southcentral Alaska, collected September 19, 2023: Raw Data File RDF 2025-8, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 9 p

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
    Not applicable
  2. How accurate are the geographic locations?
    Horizontal accuracy was not measured for this collection; it is considered inherent in the airborne GPS/IMU solution.
  3. How accurate are the heights or depths?
    We measured a vertical mean offset of +77.2 cm between 54 control points and the point cloud. This offset was reduced to -3 cm by applying a constant vertical correction to the lidar point data. We used 15 checkpoints to determine the non-vegetated vertical accuracy (NVA) of the point cloud ground class, using a tin-based approach. Project NVA was calculated to have a root mean square error (RMSE) of 20 cm. Relative accuracy was evaluated based on interswath overlap consistency, yielding an RMSE of 2.3 cm.
  4. Where are the gaps in the data? What is missing?
    This is a full-release dataset. There was no over-collect.
  5. How consistent are the relationships among the observations, including topology?
    Data quality is consistent throughout the survey, save for gaps over bodies of water, glaciers, and snow-covered surfaces.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
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.
  1. Who distributes the data set? (Distributor 1 of 1)
    Alaska Division of Geological & Geophysical Surveys
    Metadata Manager
    3354 College Road
    Fairbanks, AK
    USA

    (907)451-5020 (voice)
    (907)451-5050 (FAX)
    dggspubs@alaska.gov
    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
    Contact_Instructions:
    Please 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.
  2. What's the catalog number I need to order this data set? RDF 2026-5
  3. What legal disclaimers am I supposed to read?
    The State of Alaska makes no expressed 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.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 30-Jan-2026
Metadata author:
Alaska Division of Geological & Geophysical Surveys
Attn: Simone Montayne
Metadata Manager
3354 College Road
Fairbanks, AK
USA

(907)451-5020 (voice)
(907)451-5050 (FAX)
dggspubs@alaska.gov
Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

Generated by mp version 2.9.50 on Fri Jan 30 15:33:47 2026