High-resolution lidar data for infrastructure corridors, Mount Hayes Quadrangle, Alaska

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Frequently-anticipated questions:

What does this data set describe?

Title:
High-resolution lidar data for infrastructure corridors, Mount Hayes 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. This shapefile identifies areas where lidar points have been classified as snow or where snow was thought to exist based on evaluation of bare-earth DEM's and intensity images.
Supplemental_Information:
Information about accuracy and quality of lidar data can be found in quality control reports provided by DOGAMI and delivery reports provided by Watershed Sciences, Inc. Individual reports were provided for each delivery set and have been combined by DGGS into comprehensive quality control and delivery reports. These documents are organized by according to how data were delivered to DGGS. A description of information pertaining to down-loadable files can be found in the quality control and delivery reports. 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. This dataset is described as a single layer. Attribute information for the layer is included in this metadata file under the "Entity_and_Attribute_Information" section. The layer is titled: 
snow:	Polygons representing areas of snow
  1. How should this data set be cited?

    Hubbard, T.D., Braun, M.L., Westbrook, R.E., and Gallagher, P.E., 2011, High-resolution lidar data for infrastructure corridors, Mount Hayes Quadrangle, Alaska: Raw Data File RDF 2011-3A, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys, Fairbanks, Alaska USA.

    Online Links:

    This is part of the following larger work.

    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: -145.872802
    East_Bounding_Coordinate: -145.531953
    North_Bounding_Coordinate: 63.738310
    South_Bounding_Coordinate: 63.171531

  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 vector 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: -147.000000
      Latitude_of_Projection_Origin: 0.000000
      False_Easting: 500000.000000
      False_Northing: 0.000000

      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.

  7. How does the data set describe geographic features?

    rdf2011-3-snow
    Polygons representing areas of snow. (Source: this report)

    snow
    Indicates level of certainty associated with polygons representing areas of snow (Source: Department of Natural Resources, Division of Geological & Geophysical surveys and Watershed Sciences, Inc.)

    ValueDefinition
    classedAreas of snow with valid ground points below
    suspectedAreas indicative of snow without valid ground points below. Snow was identified based on the patterns of the intensity returns

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 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?

Shapefile meant to identify areas within the lidar dataset that may contain snow. Ground elevations may be less accurate in areas of snow.

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 6)
    Acquisition: The lidar data were collected between September and October 2010 and between May and July 2011. The survey used the Leica ALS60 system. Near-nadir scan angles were used to increase penetration of vegetation to ground surfaces. Ground-level GPS and aircraft IMU were collected during the flight.

    Date: 2010 (process 2 of 6)
    Processing lidar data: (1) Flight lines and data were reviewed to ensure complete coverage of the study area and positional accuracy of the laser points. (2) Laser point-return coordinates were computed using ALS Post Processor software, IPAS Pro GPS/INS software, and Waypoint GPS, based on independent data from the lidar system, IMU, and aircraft. (3) The raw lidar file was assembled into flight lines per return with each point having an associated x, y, and z coordinate. (4) Visual inspection of swath-to-swath laser point consistencies in the study area were used to perform manual refinements of system alignment. (5) Custom algorithms were designed to evaluate points between adjacent flight lines. Automated system alignment was computed based on randomly selected swath-to-swath accuracy measurements that consider elevation, slope, and intensities. Specifically, refinement in the combination of system pitch, roll, and yaw-offset parameters optimize internal consistency. (6) Noise (e.g., pits and birds) was filtered using ALS post processing software, based on known elevation ranges, and included the removal of any cycle slips.

    Date: 2010 (process 3 of 6)
    Creation of bare-earth DEMs: (1) The TerraScan software suite was used to classify near-ground points. Geometric constraints were used to remove all points not near the earth. The resulting bare-earth ground model was then visually inspected and additional ground modeling was performed in site-specific areas to improve ground detail. (2) The corrected and filtered return points were compared to the real-time kinematic (RTK) ground survey points collected to verify the vertical and horizontal accuracies. (3) Points were output as laser points, TINed and GRIDed.

    Date: 2010 (process 4 of 6)
    Creation of lidar intensity images: (1) Laser points were then broken into tiles related to their quadrangle and output as GeoTiffs, colored (0-255) by intensity value.

    Date: 2011 (process 5 of 6)
    Bare earth DEMs and intensity images were used to identify areas of potential snow. In some areas of the project, snow could not be avoided during acquisition. Lidar returns that were identifiable as snow were reclassified into a new "snow" class. In areas where snow completely obstructed the ground, snow points were retained in the ground model to avoid expansive interpolation across snow fields. In areas where snow prevented laser penetration, ground elevations may be offset from the true ground. A shapefile delineating areas of snow was created. The shapefile attribution includes a field designating each area as "classified" - meaning valid ground returns exist beneath the snow, or "suspected" - meaning no valid ground returns exist, but the area was identified as snow using the return intensity pattern. Because of temporal differences in neighboring flight mission areas, a 'stair step' artifact occurs in quad XMHA4 as a result of snow melt on the river valley between June 7th and June 27th, 2011.

    Date: 2012 (process 6 of 6)
    A metadata file was created to generally describe to describe the vector polygon files delineating areas of snow within the lidar collection area. .

  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?

    The accuracy of the snow polygons is dependent on the accuracy of the collected lidar data and inspection of the bare-earth DEM's and intensity images. This shapefile is only to be used as a reference and was not evaluated for accuracy.

  2. How accurate are the geographic locations?

    Horizontal accuracy is dependant on the accuracy of the collected lidar data and the interpretations made from bare-earth DEM's and intensity imagery. Therefore the accuracy can be no greater than the accuracy of the lidar. True horizontal accuracy is regarded as a product of the lidar ground footprint. Lidar is referenced to co-acquired GPS base station data that have accuracies far greater than the value of the lidar footprint. The ground footprint is equal to 1/3333rd of the above-ground flying height. The ground footprint for data collected for this project exceeds typical accuracy of ground control used to reference the lidar data (less than 0.01 meters). Project specifications require the lidar footprint to be between 0.15 and 0.40 meters. Refer to the lidar QC report and lidar delivery report for additional information on horizontal accuracy for individual delivery areas.

  3. How accurate are the heights or depths?

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

    Snow polygons were not checked for completeness. Polygons are only meant to be used as a reference in areas where there was detectable snow cover.

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

    Lidar DEM's and intensity images were inspected to be consistent when identifying areas of snow. See process steps for more detail.

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 2011-3A

  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?

Who wrote the metadata?

Dates:
Last modified: 26-Jul-2012
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:

Generated by mp version 2.9.2 on Thu Jul 26 11:24:15 2012