High-resolution lidar data for Alaska infrastructure corridors

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Frequently-anticipated questions:


What does this data set describe?

Title: High-resolution lidar data for Alaska infrastructure corridors
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. This dataset is the real-time kinematic (RTK) data collected during lidar data acquisition. Data were used to check the accuracy of collected lidar data.
Supplemental_Information:
This metadata file has been written to document and describe, as a whole, all of the RTK data collected as a part of this project. Specific information about accuracy and quality of RTK data can be found in delivery reports provided by Watershed Sciences, Inc. Individual reports were provided for each delivery set and have been combined by DGGS into a comprehensive delivery report. The delivery report document is organized according to how data were delivered to DGGS. A description of information pertaining to downloadable files can be found in the delivery reports. The DGGS metadata standard extends the FGDC standard to also include several elements that are required to facilitate our internal data management. These elements relate individual data items to a common dataset. This dataset describes a single layer titled:
rtk: Real time kinematic (RTK) check points for data accuracy
  1. How should this data set be cited?

    Hubbard, T.D., Koehler, R.D., and Combellick, R.A., 2011, High-resolution lidar data for Alaska infrastructure corridors: Raw Data File RDF 2011-3, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys, Fairbanks, AK USA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -150.82
    East_Bounding_Coordinate: -141.00
    North_Bounding_Coordinate: 70.38
    South_Bounding_Coordinate: 61.04

  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: vector digital data, document

  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?

      The map projection used is Alaska Albers Equal Area Conic.

      Projection parameters:
      Standard_Parallel: 55
      Standard_Parallel: 65
      Longitude_of_Central_Meridian: -154
      Latitude_of_Projection_Origin: 50
      False_Easting: 0
      False_Northing: 0

      Planar coordinates are encoded using coordinate pair
      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 Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257222.

      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 0.0000001
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method: Attribute values

  7. How does the data set describe geographic features?

    rdf2011-3-rtk
    Points showing location of RTK data acquisition sites. (Source: Alaska Division of Geological & Geophysical Surveys, this report)

    Elevation
    Indicates elevation in meters. (Source: Department of Natural Resources, Division of Geological & Geophysical Surveys)

    Range of values
    Minimum:0
    Maximum:1447.585


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
    c/o James Weakland
    GIS Analyst
    3354 College Rd
    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?

Provide real time kinematic (RTK) check points for data accuracy.


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: 2010 (process 1 of 4)
    A Trimble GPS receiver model R7 with Zephyr Geodetic antenna and ground plan was deployed for all static control. Simultaneously, RTK data were collected using a Trimble model R8 GNSS unit. The surveyor begins collecting data after remaining stationary for 5 seconds, then calculating the pseudo range position from at least three epochs with the relative error under 1.5 cm horizontal and 2 cm vertical. All GPS measurements were made with dual frequency L1-L2 receivers with carrier-phase correction. RTK positions were collected on bare earth locations such as paved, gravel or stable dirt roads, and other locations where the ground was clearly visible (and likely to remain visible) from the sky during the data acquisition and RTK measurement period(s). In order to facilitate comparisons with lidar measurements, RTK measurements were not taken on highly reflective surfaces such as center line stripes or lane markings on roads. RTK points were taken no closer than one meter to any nearby terrain breaks such as road edges or drop offs.

    Date: 2010 (process 2 of 4)
    Collected RTK data was post processed along with reference data and CORS data. Refer to the delivery report for more information about the RTK survey collection and data processing techniques. Final survey RTK data for each delivery were output to a point shapefile.

    Date: 2012 (process 3 of 4)
    All RTK shapefiles for each delivery were combined into a single shapefile containing all of the RTK data. Data were reprojected in Alaska Albers Equal Area Conic.

    Date: 2012 (process 4 of 4)
    A metadata file was created to generally describe the acquisition of RTK files for the entire project.

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


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

  1. How well have the observations been checked?

    RTK data were collected during periods when Point Dilution of Precision (PDOP) was less than or equal to 3, and with at least 6 satellites in view of both a stationary reference receiver and the roving receiver. The surveyor begins collecting data after remaining stationary for 5 seconds, then calculating the pseudo range position from at least 3 epochs with the relative error under 1.5 cm horizontal and 2 cm vertical. RTK measurements were not taken on highly reflective surfaces and were taken no closer than one meter to any nearby terrain breaks. Static GPS data from the reference receiver were processed using triangulation with Continuously Operating Reference Stations (CORS). Please refer to the lidar delivery report for details about the survey accuracy for individual datasets.

  2. How accurate are the geographic locations?

    The RTK data is accurate to 1.5 cm or less.

  3. How accurate are the heights or depths?

    The RTK data is accurate to 2 cm or less.

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

    RTK data have been checked for accuracy and completeness. Please refer to the lidar delivery report and lidar QC report for details about data completeness for individual delivery sets.

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

    RTK GPS surveying involves using a GPS base station deployed over a known monument with a radio connection to a GPS rover. Both the base station and rover receive differential GPS data and a baseline correction is resolved between the two.


How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints:
This 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)

    State of Alaska, Department of Natural Resources, 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 2011-3

  3. What legal disclaimers am I supposed to read?

    The State of Alaska makes no express or implied warranties (including warranties of merchantability and fitness) with respect to the character, function, or capabilities of the electronic services 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, any failure thereof, or otherwise, and 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?

  5. Is there some other way to get the data?

    DGGS publications are available as free online downloads or you may purchase paper hard-copies or digital files on CD/DVD or other digital storage media over the counter, by mail, phone, fax, or email from the DGGS Fairbanks office. Turnaround time is 1-2 weeks unless special arrangements are made and an express fee is paid. Shipping charge will be the actual cost of postage and will be added to the total amount due. Contact us for exact shipping amount.


Who wrote the metadata?

Dates:
Last modified: 29-May-2012
Metadata author:
Metadata manager
State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys
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:


Generated by mp version 2.9.6 on Tue May 29 15:45:45 2012