Lidar-derived elevation data for Kensington Mine, Southeast Alaska

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Frequently anticipated questions:


What does this data set describe?

Title:
Lidar-derived elevation data for Kensington Mine, Southeast Alaska
Abstract:
The State of Alaska Division of Geological & Geophysical Surveys (DGGS) used lidar to produce a digital terrain model (DTM) and digital surface model (DSM) of Kensington Mine, southeast Alaska, during snow-free ground conditions. The lidar and Global Navigation Satellite System (GNSS) data were collected on September 7, 2019, and processed using Terrasolid. This data collection is being released as a Raw Data File with an open end-user license. All files can be downloaded free of charge from the Alaska Division of Geological & Geophysical Surveys website (http://doi.org/10.14509/30470).
Supplemental_Information:
classified point cloud data: Classified point cloud data is provided in this collection in compressed .laz format. Data are classified in accordance with ASPRS 2014 guidelines and contain return and intensity information. 
digital surface model: The DSM represents surface elevations, for example, heights of vegetation, buildings, bridges, etc. The DSM is a single band, 32-bit GeoTIFF file, with a ground sample distance of 0.5 meters. No Data value is set to -3.40282306074e+038.
digital terrain model: The DTM represents surface elevations of ground surfaces, excluding vegetation, bridges, buildings, etc. The DTM is a single-band, 32-bit float GeoTIFF file, with a ground sample distance of 0.5 meter. No Data value is set to -3.40282306074e+038. 
lidar intensity image: 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 with a ground sample distance of 0.5 meters. No Data value is set to -3.40282306074e+038 (32-bit, floating-point minimum).
  1. How might this data set be cited?
    Wikstrom Jones, Katreen, Wolken, G.J., Daanen, R.P., and Herbst, A.M., 2020, Lidar-derived elevation data for Kensington Mine, Southeast Alaska: Raw Data File RDF 2020-7, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 5 p.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -135.079056
    East_Bounding_Coordinate: -135.019158
    North_Bounding_Coordinate: 58.879165
    South_Bounding_Coordinate: 58.821644
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 07-Sep-2019
    Ending_Date: 24-Oct-2019
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: imagery
  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: 8
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -135
      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 North American Datum of 1983 (2011).
      The ellipsoid used is GRS 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257222101000025.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: NAVD88, GEOID12B
      Altitude_Resolution: 0.5
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    classified point cloud data
    Classified point cloud data is provided in this collection in compressed .laz format. Data are classified in accordance with ASPRS 2014 guidelines and contain return and intensity information. (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))
    digital surface model
    The DSM represents surface elevations, for example, heights of vegetation, buildings, bridges, etc. The DSM is a single band, 32-bit GeoTIFF file, with a ground sample distance of 0.5 meters. No Data value is set to -3.40282306074e+038. (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))
    digital terrain model
    The DTM represents surface elevations of ground surfaces, excluding vegetation, bridges, buildings, etc. The DTM is a single-band, 32-bit float GeoTIFF file, with a ground sample distance of 0.5 meter. No Data value is set to -3.40282306074e+038. (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))
    lidar intensity image
    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 with a ground sample distance of 0.5 meters. No Data value is set to -3.40282306074e+038 (32-bit, floating-point minimum). (Source: Alaska Division of Geological & Geophysical Surveys (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 U.S. Geological Surveys, Kensington Mine (Coeur Mining) and Alaska Department of Natural Resources, Division of Geological & Geophysical Surveys. We thank Coastal Helicopters 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

Why was the data set created?

The goal of the survey is to provide snow-free surface elevations for the purpose of deriving snow depth distribution models with repeat surveys during snow-covered surface conditions. This data release is one of a series of DGGS publications to present elevation data.

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: 07-Sep-2019 (process 1 of 4)
    Data acquisition - This lidar survey was flown on September 7, 2019 at an average elevation of 130 m above ground level and a ground speed of approximately 30 m/s with a helicopter configuration, using a Bell 206 JetRanger. Elevation data were acquired with a Riegl VUX1-LR laser scanner integrated with a GNSS and Northrop Grumman IMU system. The integration was designed by Phoenix LiDAR systems. Lidar data were acquired at a pulse rate ranging from 50,000 pulses per second in the alpine areas to 400,000 pulses per second over forested areas, a scan rate of 200 revolutions per second, and a scan angle range of 80-280 degrees.
    Date: 24-Oct-2019 (process 2 of 4)
    Ground survey - Ground control and checkpoints were collected on October 24, 2019. A Trimble R7 GNSS receiver with Zephyr-2 antenna was deployed near the center of the study area. It provided a base station occupation and real-time kinematic (RTK) corrections to points surveyed with a rover Trimble R8-4 GNSS receiver (internal antenna). 76 ground control points and checkpoints were collected to be used for calibration and assessment of the vertical accuracy of the point cloud. All points were collected on a paved road surface.
    Date: 2020 (process 3 of 4)
    Point classification - Raw data were processed using Terrasolid software to produce integrated files for navigation correction and a point cloud for calibration. The navigation was corrected using Inertial Explorer software. The software integrates the GNSS and IMU data to establish the correct flight path and orientation of the lidar sensor. Internal consistency within the dataset was improved by calibrating the point cloud data using global, flight line, and fluctuation (within individual flightlines) tielines in TerraSolid software. The point cloud data were classified for ground points as well as low, medium, and high vegetation (0.01-0.5 m, 0.5-3 m, and 3-60 m heights above the ground, respectively). Some manual processing was required to eliminate erratically placed points and misclassified ground points. All low points and air points were eliminated from the dataset.
    Date: 2020 (process 4 of 4)
    Raster products - A LAS dataset was created in ArcMap, from which a 50-cm DTM, 50-cm DSM, and 1-m intensity image were produced. The DTM was derived from elevation values of Ground-classified points only and built using the binning technique of minimum elevation and linear void fill. The DTM was derived from elevation values from first returns from the Grounds, Low Vegetation, Medium Vegetation, or High Vegetation classes, and built using the binning technique of average elevation values and linear void fill. The intensity image was derived from the intensity values of the first return points.
  3. What similar or related data should the user be aware of?
    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?
    Horizontal accuracy was not measured for this collection.
  3. How accurate are the heights or depths?
    The elevation values of 59 ground control points were compared with the elevation values of the lidar points classified as Grounds. The average vertical offset was corrected with a z-transformation. 16 checkpoints were used to determine the final accuracy of the z-transformed lidar point cloud. The lidar point cloud had a vertical offset of +14.4 cm (Root mean squared error [RMSE] 18.7 cm) compared to ground control; therefore, a vertical transformation of -14.4 cm was applied to the lidar point cloud. The final accuracy assessment showed a mean vertical offset of -8.24 cm and RMSE of 17.6 cm. Relative accuracy for this dataset was evaluated as the interswath overlap consistency and was measured at 0.56 cm RMSE. A table of checkpoints and errors is provided in the accompanying report.
  4. Where are the gaps in the data? What is missing?
    This data release is complete, and there is no over collect, except for the aircraft turns that were eliminated from the dataset.
  5. How consistent are the relationships among the observations, including topology?
    There are a few areas where data coverage is limited due to laser range exceedance, which is related to the slow response of the fixed-wing aircraft to the fast elevation change along the flight path (e.g., in canyons). Relative accuracy for this dataset was evaluated as the interswath overlap consistency and was measured at 0.56 cm RMSE. The accompanying report provides additional detail regarding tests used to determine data fidelity.

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
  2. What's the catalog number I need to order this data set? RDF 2020-7
  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: 18-Nov-2020
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 Wed Nov 18 19:29:56 2020