Lidar-derived elevation data for Blackerby parcel, Juneau, southeast Alaska, collected July 12, 2023

Metadata also available as - [Parseable text] - [XML]

Frequently anticipated questions:


What does this data set describe?

Title:
Lidar-derived elevation data for Blackerby parcel, Juneau, southeast Alaska, collected July 12, 2023
Abstract:
Lidar-derived elevation data for Blackerby parcel, Juneau, southeast Alaska, collected July 12, 2023, Raw Data File 2024-8 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 slopes above the Blackerby Parcel in Juneau, Southeast Alaska, during leaf-on conditions. The survey provides snow-free surface elevations for use in landslide hazard assessment, geologic mapping, and slope-stability analysis. Ground control data provided by the Alaska Department of Transportation (DOT) was collected on March 21, 2017. DGGS collected aerial lidar data on July 12, 2023, and subsequently merged and processed using a suite of 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/10.14509/31161).
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 all ground points, the average point spacing is 48.4 cm, and the average density is 4.27 pts/m2	
dsm:    The DSM represents surface elevations, including heights of vegetation, buildings, powerlines, bridge decks, etc. It is a single-band, 32-bit GeoTIFF file of 20-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, bridge decks, buildings, etc. The DTM is a single-band, 32-bit GeoTIFF file of 20-cm 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 (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.
  1. How might this data set be cited?
    Zechmann, J.M., Larsen, M.C., and Wikstrom Jones, K.M., 2025, Lidar-derived elevation data for Blackerby parcel, Juneau, southeast Alaska, collected July 12, 2023: Raw Data File RDF 2024-8, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 8 p.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -134.500809
    East_Bounding_Coordinate: -134.448702
    North_Bounding_Coordinate: 58.360206
    South_Bounding_Coordinate: 58.326341
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 01-Mar-2017
    Ending_Date: 12-Jul-2023
    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: 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 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. Also includes footprints for tiled data. (Source: DGGS)
    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 all ground points, the average point spacing is 48.4 cm, and the average density is 4.27 pts/m2 (Source: DGGS)
    dsm
    The DSM represents surface elevations, including heights of vegetation, buildings, powerlines, bridge decks, etc. It is a single-band, 32-bit GeoTIFF file of 20-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, bridge decks, buildings, etc. The DTM is a single-band, 32-bit GeoTIFF file of 20-cm 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 (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. (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?
    This survey area is located within the traditional homelands of the A'akw Kwaan and T'aaḵu Ḵwaan Tlingit peoples. This work was funded by the Alaska Division of Mining, Land, and Water (Reimbursable Services Agreement-IPO 230001027). We thank Clearwater Air for their aviation expertise and contribution to these data products and the Alaska Department of Transportation for providing ground control points. The views and conclusions contained in this document are those of the authors. They should not be interpreted as necessarily representing the State of Alaska's official policies, either expressed or implied.
  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?

The data were collected during leaf-on conditions and provides snow-free surface elevations useful for landslide hazard analysis.

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: 01-Mar-2017 (process 1 of 3)
    Ground survey - The Alaska Department of Transportation collected ground control points along the centerline of Glacier Highway in Juneau on March 21, 2017. They deployed a Leica GS-15 for static GPS control for points they surveyed with a Leica TS15 total station. DOT collected 36 ground control points and checkpoints (all located on paved surfaces), which we use for calibration and to assess the vertical accuracy of the point cloud.
    Date: 12-Jul-2023 (process 2 of 3)
    Aerial survey - DGGS used a Riegl VUX1-LR22 laser scanner integrated with a global navigation satellite system (GNSS) and Northrop Grumman LN-200C inertial measurement unit (IMU) designed 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 a range of 1000 m (ranges assume approximately 20 percent natural reflectance). The scanner operated with a pulse refresh rate of 600,000 pulses per second, with a scan rate of 200 lines per second. We used a Cessna 180 fixed-wing platform to survey from an elevation of approximately 150 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 survey area covers approximately 7.4 km2. The survey area was accessed by air from Juneau International Airport. Data collection began at 1:40 p.m. (AST) and ended at 2:00 p.m. (AST). The weather was partly cloudy with no wind.
    Date: 2024 (process 3 of 3)
    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. We created macros in Terrasolid software and classified points in accordance with the American Society for Photogrammetry & Remote Sensing (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 20-cm DSM was interpolated from maximum-return values from ground, vegetation, bridge deck, and building classes using a binning method and maximum values. A 20-cm DTM was interpolated from all ground-class returns using a binning method and minimum values. We also produced a 20-cm intensity image for the entire 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?
    Nicolsky, D.J., Suleimani, E.N., Koehler, R.D., and Salisbury, J.B., 2017, Tsunami inundation maps for Juneau, Alaska: Report of Investigation RI 2017-9, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 66 p., 5 sheets
    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
    Wikstrom Jones, K.M., and Wolken, G.J., 2022, Lidar-derived elevation data for Mount Juneau, Southeast Alaska, collected September 6, 2019: Raw Data File RDF 2021-12, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 8 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?
    Horizontal accuracy was not measured for this collection.
  3. How accurate are the heights or depths?
    We measured a mean offset of +68.3 cm between 23 control points and the point cloud. This offset was reduced to +0.1 cm by applying a static vertical correction to the lidar point data. We used 13 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 3.9 cm. We evaluated the relative accuracy for this dataset as the interswath overlap consistency and measured it at 8.4 cm RMSE.
  4. Where are the gaps in the data? What is missing?
    This is a full-release dataset.
  5. How consistent are the relationships among the observations, including topology?
    DGGS visually inspected the orthoimage for data errors such as shifts, seamline mismatches, and water noise overlapping land. There were no significantly erroneous areas that required repair. Data quality is consistent throughout the survey. There was no over-collect.

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 2024-8
  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: 23-Jan-2025
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 Jan 23 18:57:56 2025