Lidar-derived elevation data for Columbia Glacier terminus and adjacent slope, Southcentral Alaska, collected September 18, 2022

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Frequently anticipated questions:


What does this data set describe?

Title:
Lidar-derived elevation data for Columbia Glacier terminus and adjacent slope, Southcentral Alaska, collected September 18, 2022
Abstract:
Lidar-derived elevation data for Columbia Glacier terminus and adjacent slope, Southcentral Alaska, collected September 18, 2022, Raw Data File 2023-16, provides an aerial lidar derived classified point cloud, a digital terrain model (DTM), and an intensity model of the unstable slope at the terminus of Columbia Glacier, located in Prince William Sound in Southcentral Alaska. Aerial and ground control data were collected on September 18, 2022, and subsequently processed in a suite of geospatial processing software. These data support a paraglacial rock slope destabilization study at Columbia Glacier and will be used to assess and characterize an ongoing landslide hazard. All files can be downloaded from the Alaska Division of Geological & Geophysical Surveys website (http://doi.org/10.14509/31032).
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 compressed LAZ format. This dataset only includes ground points and unclassified points; low- and high-noise points are excluded. Potential vegetation points remain within the unclassified points class. For classified ground points, the average point density is 13.9 points/m2.	
dtm:    The DTM represents bare earth elevations, excluding vegetation, bridges, buildings, etc. The DTM is a single-band, 32-bit float GeoTIFF file of 0.20-meter 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 largely a function of scanned object reflectance in relation to the signal frequency, is dependent on ambient conditions, and is not necessarily consistent between separate scans. The intensity image is a single-band, 32-bit float GeoTIFF file of 0.5-meter resolution. No Data value is set to -3.40282306074e+38.
  1. How might this data set be cited?
    Wikstrom Jones, K.M., Wolken, G.J., and Daanen, R.P., 2023, Lidar-derived elevation data for Columbia Glacier terminus and adjacent slope, Southcentral Alaska, collected September 18, 2022: Raw Data File RDF 2023-16, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 11 p.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -147.040293
    East_Bounding_Coordinate: -146.921476
    North_Bounding_Coordinate: 61.226991
    South_Bounding_Coordinate: 61.177871
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 22-Sep-2022
    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: 0.001
      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. also includes footprints for tiled data. (Source: DGGS)
    classified_points
    Classified point cloud data are provided in compressed LAZ format. This dataset only includes ground points and unclassified points; low- and high-noise points are excluded. Potential vegetation points remain within the unclassified points class. For classified ground points, the average point density is 13.9 points/m2. (Source: DGGS)
    dtm
    The DTM represents bare earth elevations, excluding vegetation, bridges, buildings, etc. The DTM is a single-band, 32-bit float GeoTIFF file of 0.20-meter resolution. No Data value is set to -3.40282306074e+38. (Source: DGGS)
    lidar_intensity
    The lidar intensity image describes the relative amplitude of reflected signals contributing to the point cloud. Lidar intensity is largely a function of scanned object reflectance in relation to the signal frequency, is dependent on ambient conditions, and is not necessarily consistent between separate scans. The intensity image is a single-band, 32-bit float GeoTIFF file of 0.5-meter resolution. No Data value is 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 a U.S. Geological Survey Cooperative Agreement (Grant Number G21AC10362-00) and the State of Alaska and collected and processed by DGGS. We thank Clearwater Air 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.
  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 data support a paraglacial rock slope destabilization study at Columbia Glacier and will be used to assess and characterize an ongoing landslide hazard.

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: 18-Sep-2022 (process 1 of 3)
    Ground survey - Ground control and check points were collected on September 18, 2022. We deployed a Trimble R10-2 GNSS receiver with an internal antenna at a temporary benchmark at a centralized location within the survey area (61 degrees 12 minutes 37.84428 seconds N; 146 degrees 57 minutes 58.96235 seconds W). It provided a base station occupation and real-time kinematic (RTK) corrections to points we surveyed with a rover Trimble R10-2 GNSS receiver (internal antenna). A total of 82 ground control and check points were collected to use for calibration and to assess the vertical accuracy of the point cloud. All points were collected on bare earth.
    Date: 18-Sep-2022 (process 2 of 3)
    Aerial 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). The lidar integration system was designed by Phoenix LiDAR Systems. The sensor can collect up to 820,000 points per second at a range of up to 150 m. The scanner operated with a pulse repetition rate of 100,000-400,000 pulses per second at a scan rate between 80 and 160 revolutions per second. We used a Cessna 180 fixed-wing platform to survey from an elevation of about 100-500 m above ground level, at a ground speed of ~37 m/s, and with a scan angle set from 80 to 280 degrees. The total survey area covers ~14 km2. We flew the aerial survey on September 18, 2022, beginning at 10:21 am and ending at 11:57 am (AKDT). The weather throughout the survey was clear, with still winds.
    Date: 2023 (process 3 of 3)
    Lidar dataset processing - The point data were processed 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. The IMU and GNSS data were processed in Inertial Explorer, and Spatial Explorer software was used to integrate flightline information with the point cloud. 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 nominal point density is 31.4 points/m2 and the average nominal pulse spacing is 17.9 cm. We created macros in Terrasolid software and classified points in accordance with the American Society for Photogrammetry and Remote Sensing (ASPRS) 2019 guidelines. Once classified, we applied a geometric transformation and converted the points from ellipsoidal heights to GEOID12B (Alaska) orthometric heights. ArcGIS Pro was used to derive raster products from the point cloud. The 0.20-meter DTM was interpolated from all ground class returns using a triangulated-irregular network (TIN) method and minimum values. In ArcGIS Pro, we produced a 0.5-meter intensity image by binning and averaging ground and unclassified points, which include vegetation points.
  3. What similar or related data should the user be aware of?
    Stevens, D.S.P., Wolken, G.J., Hubbard, T.D., and Hendricks, K.A., 2018, Landslides in Alaska: Information Circular IC 65, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 2 p
    Timm, Kristin, and Wolken, G.J., 2017, Deglacierization and the development of glacier-related hazards: Information Circular IC 63, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 3 p
    Wolken, G.J., Hendricks, K.A., Daanen, R.P., Overbeck, J.R., Stevens, D.S.P., and Masterman, S.S., 2017, Alaska & climate change: Information Circular IC 64, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 2 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?
    We did not measure horizontal accuracy for this collection.
  3. How accurate are the heights or depths?
    A mean vertical offset of 19.8 cm was measured between 64 control points and the point cloud. A final accuracy of -6.4 cm was achieved by performing a vertical transformation of the lidar point data. Eighteen check points were used to determine the non-vegetated vertical accuracy of the point cloud ground class, using a Triangulated Irregular Network (TIN)-based approach, and a root mean square error (RMSE) of 13.4 cm was achieved. We evaluated the relative accuracy for this dataset as the interswath overlap consistency and measured it at 1.9 cm RMSE.
  4. Where are the gaps in the data? What is missing?
    This data relaease is complete.
  5. How consistent are the relationships among the observations, including topology?
    This publication is a complete release dataset. There was no over-collect except for aircraft turns that were eliminated from the dataset. The data quality is consistent throughout the survey.

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 2023-16
  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: 08-Feb-2024
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 Thu Feb 08 20:09:29 2024