High-resolution lidar data for infrastructure corridors, Talkeetna Mountains Quadrangle, Alaska

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Frequently anticipated questions:


What does this data set describe?

Title:
High-resolution lidar data for infrastructure corridors, Talkeetna Mountains Quadrangle, Alaska
Abstract:
In advance of design, permitting, and construction of a pipeline to deliver North Slope natural gas to out-of-state customers and Alaska communities, the Division of Geological & Geophysical Surveys (DGGS) has acquired LiDAR (Light Detection and Ranging) data along proposed pipeline routes, nearby areas of infrastructure, and regions where significant geologic hazards have been identified. LiDAR data will serve multiple purposes, but have primarily been collected to (1) evaluate active faulting, slope instability, thaw settlement, erosion, and other engineering constraints along proposed pipeline routes, and (2) provide a base layer for the state-federal GIS database that will be used to evaluate permit applications and construction plans. The dataset represents all classified laser returns from the LiDAR survey and their associated geospatial coordinates.
Supplemental_Information:
This metadata file was written to document and describe, as a whole, all of the classified laser returns (point cloud data) generated for this project. It provides a brief overview of the data acquisition, processing, and quality control steps utilized by DGGS contractors and subcontractors. We encourage users to review the delivery and quality control reports provided by Watershed Sciences, Inc. (WSI) and Oregon Department of Geology and Mineral Industries (DOGAMI) for a comprehensive discussion of their processes. These reports can be found on the citation page for this publication. The DGGS metadata standard extends the FGDC standard to include elements that are required to facilitate our internal data management. These elements, referred to as "layers," group and describe files that have intrinsic logical or topological relationships. Attribute information for the layers (entity) is included in this metadata file under the "Entity_and_Attribute_Information" section. The layers are titled: >Point-cloud data - all returns - classified:Classified (ASPRS standard) LiDAR attributes for all returns >Point-cloud data - ground returns - classified:Classified (ASPRS standard) LiDAR attributes for ground returns
  1. How should this data set be cited?

    Hubbard, T.D., Koehler, R.D., and Combellick, R.A., 2011, High-resolution lidar data for infrastructure corridors, Talkeetna Mountains Quadrangle, Alaska: Raw Data File RDF 2011-3N, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 291 p.

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -150
    East_Bounding_Coordinate: -147
    North_Bounding_Coordinate: 63
    South_Bounding_Coordinate: 62

  3. What does it look like?

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 2010
    Ending_Date: 2011
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: LAS

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a point 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 row and column
      Abscissae (x-coordinates) are specified to the nearest 0.000001
      Ordinates (y-coordinates) are specified to the nearest 0.000001
      Planar coordinates are specified in meters

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is North American Datum of 1983.
      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: North American Vertical Datum of 1988
      Altitude_Resolution: 0.000001
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method: Attribute values

  7. How does the data set describe geographic features?

    all_points
    Data type: Point-cloud data - all returns - classified; Description: Classified (ASPRS standard) LiDAR attributes for all returns; File format: LAS v 1.2 (Source: Watershed Sciences, Inc.)

    ground_points
    Data type: Point-cloud data - ground returns - classified; Description: Classified (ASPRS standard) LiDAR attributes for ground returns; File format: LAS v 1.2 (Source: Watershed Sciences, Inc.)


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?

    Data collection was supported by funding from the Department of Natural Resources (DNR), Division of Geological & Geophysical Surveys (DGGS), the Alaska Gas Pipeline Project Office, the Office of the Federal Coordinator, and the Alaska Gasline Development Corporation (AGDC). LiDAR data were collected and processed by Watershed Sciences, Inc. of Corvallis, OR. Survey data were collected by McClintock Land Associates of Eagle River, AK. LiDAR data and derivative products were checked for quality, completeness, and accuracy by State of Oregon Department of Geology & Mineral Industries based in Portland, OR.

  3. To whom should users address questions about the data?

    Alaska Division of Geological & Geophysical Surveys
    Attn: James Weakland
    GIS Analyst
    3354 College Road
    Fairbanks, AK 99709-3707
    USA

    (907)451-5029 (voice)
    dggsgis@alaska.gov

    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays


Why was the data set created?

In advance of design, permitting, and construction of a pipeline to deliver North Slope natural gas to out-of-state customers and Alaska communities, the Division of Geological & Geophysical Surveys (DGGS) has acquired LiDAR (Light Detection and Ranging) data along proposed pipeline routes, nearby areas of infrastructure, and regions where significant geologic hazards have been identified. LiDAR data will serve multiple purposes, but have primarily been collected to (1) evaluate active faulting, slope instability, thaw settlement, erosion, and other engineering constraints along proposed pipeline routes, and (2) provide a base layer for the state-federal GIS database that will be used to evaluate permit applications and construction plans. Steep slopes with poor access, combined with dense vegetation and a thick moss ground-cover that obscures the bedrock surface, make the use of LiDAR one of the most effective ways to map the geology and evaluate unstable slopes and other hazards.


How was the data set created?

  1. From what previous works were the data drawn?

    ASPRS, 2008 (source 1 of 1)
    The American Society for Photogrammetry & Remote Sensing (ASPRS), 02092008, LAS Specification Version 1.2.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution: point classification categories

  2. How were the data generated, processed, and modified?

    Date: 2010 (process 1 of 4)
    Data acquisition and processing - This LiDAR dataset was collected and processed by WSI and their survey subcontractor, McClintock Land Associates (October 21-25, 2012). WSI has provided a delivery report which outlines in detail their data acquisition procedures, processing methods, and results of all accuracy assessments. The delivery report is available on the citation page for this publication.

    Date: 2011 (process 2 of 4)
    Point-cloud data - all returns - classified - LiDAR data points were classified (ASPRS standard) through automated point processing algorithms and manual inspection.

    Data sources used in this process:

    • ASPRS, 2008

    Date: 2011 (process 3 of 4)
    Point-cloud data - ground returns - classified - LiDAR data points that were classified as "ground" were extracted to create the ground point data file.

    Date: 2011 (process 4 of 4)
    Quality control - WSI submitted the data to the State of Oregon Department of Geology and Mineral Industries (DOGAMI) for independent quality control analysis. After addressing any concerns from DOGAMI, WSI submitted the revised data set to DGGS along with a technical report describing details about the LiDAR acquisition, accuracy, and quality. DOGAMI also provided a separate report summarizing their methodologies and the results of quality control checks.

  3. What similar or related data should the user be aware of?

    Hubbard, T.D., Koehler, R.D., and Combellick, R.A., 2011, High-resolution LiDAR data for Alaska infrastructure corridors: Raw Data File RDF 2011-3A through RDF 2011-3T, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 291 p
    Hubbard, T.D., Wolken, G.J., Stevens, D.S.P., and Combellick, R.A., 2013, High-resolution LiDAR data for the Whittier area, Passage Canal, and Portage Lake, Alaska: Raw Data File RDF 2013-3, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 5 p


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

  1. How well have the observations been checked?

    LiDAR flight lines have been examined to ensure that there was at least 60% sidelap, there are no gaps between flight-lines, and overlapping flight-lines have consistent elevation values. Shaded relief images were visually inspected for data errors such as pits, border artifacts, gaps, and shifting. The data was examined at a 1:2000 scale. Watershed Sciences, Inc. (WSI) submitted the data to the State of Oregon Department of Geology and Mineral Industries (DOGAMI) for independent quality control analysis. After addressing any concerns from DOGAMI, WSI submitted the revised dataset to DGGS along with a technical report describing details about the LiDAR acquisition, accuracy, and quality. DOGAMI also provided a separate report summarizing their methodologies and the results of quality control checks. Both reports are available via the DGGS website.

  2. How accurate are the geographic locations?

    Horizontal accuracy refers to the ability to place laser points from multiple flight lines in the same location. Horizontal accuracy is measured as the divergence between points from overlapping flight lines. Accuracy is affected by system attitude offsets, scale and GPS/IMU drift. Manual system calibration and automated attitude calibration techniques were used to resolve divergence of data. Please see the LiDAR QC report and LiDAR delivery report for specific information about accuracy of LiDAR data.

  3. How accurate are the heights or depths?

    The vertical accuracy of the LiDAR data is described as the mean and standard deviation of divergence between LiDAR point coordinates and RTK ground survey point coordinates. To provide a sense of the model predictive power of the dataset, the root mean-square error (RMSE) for vertical accuracy is also provided. Please see the LiDAR QC report and LiDAR delivery report for specific information about accuracy and quality of LiDAR data, including a comparison of GCP elevations with bare-earth digital elevation model elevations.

  4. Where are the gaps in the data? What is missing?

    The entire dataset for this project consists of: (1) continuous 1-mile-width coverage over existing infrastructure along the entire length of the proposed natural gas pipeline corridors from Prudhoe Bay to the Canada border along the Trans-Alaska Pipeline System (TAPS) and Alaska Highway, from Delta Junction to Valdez along the TAPS, and Livengood to the Anchorage area along the George Parks Highway; (2) approximately 1-mile-wide corridors over routes the State believes gas pipeline applicants are considering, where departing from existing infrastructure; (3) half-mile-wide coverage of existing primary pipeline-support roads where outside the main corridor; and (4) expanded areas of coverage along these corridors where data are needed for evaluation of active faults, slope instability, and other hazards. The average native LiDAR pulse density was >= 8 pulses per square meter over terrestrial surfaces. It is not uncommon for some types of surfaces (e.g. dense vegetation or water) to return fewer pulses than the laser originally emitted. These discrepancies between "native" and "delivered" density will vary depending on terrain, land cover, and the prevalence of water bodies. Please see the LiDAR QC report and LiDAR delivery report for additional information.

  5. How consistent are the relationships among the observations, including topology?

    Data consistency varies slightly throughout the project area with higher errors in areas of steep terrain. The tests and processing methods used by WSI and DOGAMI to ensure data consistency are described in the accompanying delivery and quality control reports.


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
    3354 College Road
    Fairbanks, AK 99709-3707
    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 (<http://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 2011-3N

  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: 20-Aug-2013
Metadata author:
Metadata manager
3354 College Road
Fairbanks, AK 99709-3707
USA

(907)451-5020 (voice)

Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:


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