Combined high-resolution LIDAR topography and multibeam bathymetry for northern Resurrection Bay, Seward, Alaska

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Frequently-anticipated questions:

What does this data set describe?

Title:
Combined high-resolution LIDAR topography and multibeam bathymetry for northern Resurrection Bay, Seward, Alaska
Abstract:
We created a new Digital Elevation Model using the best available high-resolution topography and multibeam bathymetry surrounding the area of Seward, Alaska. Datasets of (1) LIDAR topography collected for the Kenai Watershed Forum, (2) Seward harbor soundings from the Army Corp of Engineers, (3) and NOAA multibeam bathymetry contributed to the final merged product. These datasets were placed into a common coordinate system, horizontal datum, vertical datum, and data format prior to being merged together. The projected coordinate system of Universal Transverse Mercator Zone 6 North American Datum of 1927 was used for the horizontal coordinates. Z-values in meters were referenced to the tidal datum of Mean High Water. Gaps between the datasets were interpolated to create the final seamless five-meter grid covering the area of interest around Seward, Alaska.
  1. How should this data set be cited?

    Labay, Keith A., and Haeussler, Peter J., 2008, Combined high-resolution LIDAR topography and multibeam bathymetry for northern Resurrection Bay, Seward, Alaska: U.S. Geological Survey Data Series DS 374.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -149.465478
    East_Bounding_Coordinate: -149.312773
    North_Bounding_Coordinate: 60.156298
    South_Bounding_Coordinate: 60.057664

  3. What does it look like?

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

    Beginning_Date: 2001
    Ending_Date: 2007
    Currentness_Reference: publication date

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

    Geospatial_Data_Presentation_Form: raster digital 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. It contains the following raster data types:

      • Dimensions 2141 x 1622 x 1, type Grid Cell

    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: 0.9996
      Longitude_of_Central_Meridian: -147.00
      Latitude_of_Projection_Origin: 0.00
      False_Easting: 500000
      False_Northing: 0.00

      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 5.00
      Ordinates (y-coordinates) are specified to the nearest 5.00
      Planar coordinates are specified in meters

      The horizontal datum used is North American Datum of 1927.
      The ellipsoid used is Clarke 1866.
      The semi-major axis of the ellipsoid used is 6378206.400000.
      The flattening of the ellipsoid used is 1/294.978698.

      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: Mean High Water
      Altitude_Resolution: 1
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
      Depth_System_Definition:
      Depth_Datum_Name: Mean High Water
      Depth_Resolution: 1
      Depth_Distance_Units: meters
      Depth_Encoding_Method: Explicit depth coordinate included with horizontal coordinates

  7. How does the data set describe geographic features?

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?

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

    U.S. Geological Survey
    c/o Keith A. Labay
    GIS Specialist
    4200 University Drive
    Anchorage, Alaska 99508-4667
    U.S.A.

    907-786-7410 (voice)
    klabay@usgs.gov

Why was the data set created?

This digital elevation model (DEM) was created for studying submarine landslides and tsunamis produced by the M9.2 1964 earthquake at Seward, Alaska, and for developing computer models of tsunami inundation risks as part of the National Tsunami Hazards Mitigation Program.

How was the data set created?

  1. From what previous works were the data drawn?

    multibeam bathymetry (source 1 of 3)
    NOAA National Ocean Service, 2001, National Ocean Service Office of Coast Survey Hydrographic Survey Data.

    Online Links:

    Type_of_Source_Media: online
    Source_Scale_Denominator: 10000
    Source_Contribution: Bathymetry of northern Resurrection Bay.

    Seward LIDAR (source 2 of 3)
    Forum, Kenai Watershed , unpublished, none.

    Type_of_Source_Media: DVD-ROM
    Source_Contribution: LIDAR topography of Seward, Alaska.

    Seward harbor (source 3 of 3)
    Army Corps of Engineers, unpublished, none.

    Type_of_Source_Media: text file
    Source_Contribution: Soundings of the Seward, Alaska harbor.

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

    Date: Feb-2007 (process 1 of 4)
    The Seward LIDAR data was obtained from the Kenai Watershed Forum as an ARC/INFO grid. Projection of the grid was Alaska State Plane FIPS 5004 NAD83. Z-values were in feet. The vertical datum of the Z-values was NAVD88. This grid was then reprojected into UTM Zone 6 NAD27. Z-values were converted to meters instead of feet. From the Seward tidal gages it was known that NAVD88 was 0.06 meters above Mean Lower Low Water. At Seward the difference between Mean Lower Low Water and Mean High Water is 2.96 meters, so the vertical datum was adjusted from NAVD88 to Mean High Water by adding a value of -2.9 meters. The grid was then resampled from the original 0.9144 meter cellsize to 5 meter cells. This resampled grid was then converted to a GIS point feature class.
    The extent of the Seward LIDAR data included a portion of the ocean's surface near the shoreline. This allowed a polygon to be digitized that defined the shoreline at the time the LIDAR survey was collected. Using this polygon, data points that were returned from the ocean's surface were then eliminated.
    Interpolation along the eastern and western boundaries of the grid was confined to those areas where data was collected to prevent interpolation across large areas of NODATA.

    Person who carried out this activity:

    Keith A. Labay
    4200 University Drive
    Anchorage, Alaska 99508

    907-786-7410 (voice)

    Data sources used in this process:
    • Seward LIDAR

    Data sources produced in this process:

    • ocean mask

    Date: Feb-2007 (process 2 of 4)
    The Seward harbor data was obtained from the Army Corps of Engineers as an ASCII XYZ file. Projection of the data was Alaska State Plane FIPS 5004 NAD83. Depth values were in feet. The vertical datum of the depths was Mean Lower Low Water. A GIS point feature class was created from these points and reprojected into UTM Zone 6 NAD27. Depth values were converted to meters instead of feet and values greater than or equal to zero were deleted. The vertical datum of the depths was adjusted to Mean High Water by adding a value of -2.96 meters.
    Using the remaining Seward harbor points, together with the Seward LIDAR data as a guide, a harbor mask was created to define the area where depth values would be determined from the Seward harbor points.

    Person who carried out this activity:

    Keith A. Labay
    4200 University Drive
    Anchorage, Alaska 99508

    907-786-7410 (voice)

    Data sources used in this process:
    • Seward harbor

    Data sources produced in this process:

    • harbor mask

    Date: Feb-2007 (process 3 of 4)
    The multibeam bathymetry was downloaded from the internet as an ASCII YXZ file gridded to 15 meter cells. Projection of the coordinates was UTM Zone 6 NAD83 and the depths were in positive meters. The vertical datum of the depths was Mean Lower Low Water. A GIS point feature class was created from these coordinates and the depths were changed to negative values. These points were then reprojected into UTM Zone 6 NAD27. The vertical datum of the depths was adjusted to Mean High Water by adding a value of -2.96 meters.
    Using the ocean mask defined from the Seward LIDAR data any points that fell outside of the polygon were eliminated. Points that overlapped with areas covered by the Seward harbor mask were also eliminated.

    Person who carried out this activity:

    Keith A. Labay
    4200 University Drive
    Anchorage, Alaska 99508

    907-786-7410 (voice)

    Data sources used in this process:
    • multibeam bathymetry
    • ocean mask
    • harbor mask

    Date: Feb-2007 (process 4 of 4)
    The three modified point datasets were merged together to create a single dataset. This point dataset was used to interpolate the final merged DEM. Gaps between the three datasets in the intertidal zone were filled during the interpolation process to create a seamless transition. Along the steep sides of Resurrection Bay the separation between the LIDAR data and multibeam bathymetry was minimal, and required little to no interpolation. A shallow intertidal area at the head of the bay represented the only large gap within the DEM filled during the interpolation process. Interpolation along the boundaries of the DEM was confined to those areas where data was collected to prevent interpolation edge effects. Grid cells outside of the area of interest appear as NODATA. Final projection of the merged DEM was UTM Zone 6 NAD27, Z-values were in meters, and the grid cell size was five meters.
    The grid is also provided as an ASCII comma delimited XYZ file, or a geotiff. Coordinates in the files are Geographic NAD27.

    Person who carried out this activity:

    Keith A. Labay
    4200 University Drive
    Anchorage, Alaska 99508

    907-786-7410 (voice)

    Data sources used in this process:
    • Seward LIDAR
    • Seward harbor
    • multibeam bathymetry

    Data sources produced in this process:

    • merged DEM

  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?

    See Vertical Accuracy Report

  2. How accurate are the geographic locations?

    The horizontal accuracy of this DEM has not been tested.

  3. How accurate are the heights or depths?

    The vertical accuracy of this DEM has not been tested.

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

    This DEM has been visually inspected for completeness. NODATA areas exist.

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

    The Z-values in this DEM are a composite of 3 major sources.

How can someone get a copy of the data set?

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

Access_Constraints: None
Use_Constraints:
NOT TO BE USED FOR NAVIGATION Acknowledgment of the U.S. Geological Survey would be appreciated in products derived from this data.

  1. Who distributes the data set? (Distributor 1 of 1)

    U.S. Geological Survey
    MS 902 Box 25286 Denver Federal Center
    Lakewood, CO 80225
    USA

    1-888-ASK-USGS (voice)

  2. What's the catalog number I need to order this data set?

    DS 374

  3. What legal disclaimers am I supposed to read?

    This world-wide web publication was prepared by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government of any agency thereof.

  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 09-Sep-2008
Metadata author:
U.S. Geological Survey
c/o Keith A. Labay
4200 University Drive
Anchorage, Alaska 99508

907-786-7410 (voice)
klabay@usgs.gov

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

Generated by mp version 2.9.5 on Tue Sep 09 09:50:40 2008