Bathymetric xyz data for Glacier Bay at 5-meter intervals.

Metadata also available as

Frequently-anticipated questions:


What does this data set describe?

Title: Bathymetric xyz data for Glacier Bay at 5-meter intervals.
Abstract:

This data set consists of 5-m gridded bathymetric data for Glacier Bay, Alaska, in xyz form. The data were interpolated across "nodata" gaps that were no more than 30 meters wide.

Data were collected during May 29 - June 6, 2001, by contract with Thales Geosolutions (<http://www.thales-geopacific.com/>) aboard the R/V Davidson as part of a cooperative survey conducted by the U.S. National Park Service and the U.S. Geological Survey (Biological Resources and Coastal and Marine Geology). The instrument was a Reson 8111 multibeam echosounder (<http://reson.com/sb8111.htm>). The raw data were reduced by Thales.

Supplemental_Information:

Additional information about the field activities from which this data set was derived are available online at <http://walrus.wr.usgs.gov/infobank/d/d101gb/html/d-1-01-gb.meta.html>

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Specifications for the Reson SeaBat 8111 Multibeam Echosounder (<http://www.reson.com/sb8111.htm>)

 Operating frequency:  100 kHz
 Number of beams:  101
 Beamwidth across track:  1.5 degrees
 Beamwidth along track:  1.5 degrees
 Center-to-center beam separation:  1.5 degrees
 Pulse length:  Variable, operator selectable
 Depth range:  3 - 1000 meters
 Transducer depth rating:  100 meters
 Max. update rate:  35 swaths per second
 Max. vessel Speed:  20 knots
 Stabilization:  Pitch stabilization within +/- 10 degrees
 Projector beam control:  External pitch sensor
 Hydrophone size (Dia./arc/length):  640mm, 220 degrees, 200mm
 Processor Dimensions (HWD):  177 x 483 x 434 mm
 Tranceiver Dimensions (HWD):  267 x 450 x 427 mm
 Weight: (with 15m cable):
   Hydrophone Dry: 42 kg Wet: 36 kg
   Projector Dry: 30 kg Wet: 23 kg
 Transceiver weight:  13.6 kg
 Processor weight:  20 kg
Although this Federal Geographic Data Committee-compliant metadata file is intended to document the data set in nonproprietary form, as well as in ArcInfo format, this metadata file may include some ArcInfo-specific terminology.

  1. How should this data set be cited?

    Stevenson, A.J., and Wong, Florence L. , 2002, Bathymetric xyz data for Glacier Bay at 5-meter intervals.: USGS Open-File Report 02-391, U.S. Geological Survey, Menlo Park, California.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -136.40276708
    East_Bounding_Coordinate: -135.91167668
    North_Bounding_Coordinate: 58.75728909
    South_Bounding_Coordinate: 58.35942274

  3. What does it look like?

    glacier.gif (GIF)
    index map of Glacier Bay multibeam bathymetry data

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

    Calendar_Date: 2002
    Currentness_Reference: Ground Condition

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

    Geospatial_Data_Presentation_Form: map

  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. It contains the following vector data types (SDTS terminology):

      • Point (16906963)

    2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.00004910904. Longitudes are given to the nearest 0.00004910904. Latitude and longitude values are specified in Decimal Degrees.

      The horizontal datum used is nad83.
      The ellipsoid used is GRS1980.
      The semi-major axis of the ellipsoid used is 6378206.4.
      The flattening of the ellipsoid used is 1/294.98.

  7. How does the data set describe geographic features?

    Entity_and_Attribute_Overview:
    Each record consists of three fields: longitude, latitude, and depth in meters. Example of records:

     -136.26066,58.75442,-137.124
     -136.26074,58.75438,-139.409
     -136.26066,58.75438,-137.124
     -136.26057,58.75438,-136.976
    
    Entity_and_Attribute_Detail_Citation: none


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?

    Florence L. Wong
    United States Geological Survey (USGS)
    Geologist, GIS Coordinator
    USGS, MailStop 999, 345 Middlefield Road
    Menlo Park, CA 94025-3561
    USA

    (650) 329-5327 (voice)
    (650) 329-5190 (FAX)
    fwong@usgs.gov


Why was the data set created?

These data are intended for science researchers, students, policy makers, and the general public. The data can be used with geographic information systems (GIS) software to display geologic and oceanographic information.


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: 2001 (process 1 of 4)
    Raw data processed by contractor Thales Geosolutions and provided as 10-m and 5-m xyz values in UTM 8 coordinate system.

    Date: 2001 (process 2 of 4)
    F.L. Wong converted xyz to ArcInfo grids. Data were processed in 50,000-point blocks. Each block of points was used to GENERATE a point coverage.

    The point coverage for each block was merged with adjoining blocks, the grid IDW function was applied with default options, and the resulting grid clipped to the boundary of the block. All the interpolated grids were merged into a continuous grid GLACIER05MIG that was corrected by a mask that omitted data in holes that exceed 30 meters in width.

    The masking grid was constructed as follows: a unit grid (data cells = 1, all others = nodata) was copied from a 5-m uninterpolated grid. The unit grid was converted to a polygon coverage from which polygons with areas of less than 1000 square meters were removed in bulk. The remaining interior polygons were inspected in Arcedit and removed if the width were about 30 meters or less. This polygon coverage was converted back to a grid to be applied as a mask to the merged grids described in the previous paragraph.

    Date: 2002 (process 3 of 4)
    UTM grid was converted to a point coverage by Arc tool GRIDPOINT. Point coverage was projected to decimal degrees, and longitude, latitude, and depth values extracted.

    Date: 18-Oct-2001 (process 4 of 4)
    First draft of metadata created by curator using FGDCMETA.AML ver. 1.35 08/02/2000 on ArcInfo data set /arcdata/bathymetry/glacier05mg

  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?

    Not applicable.

  2. How accurate are the geographic locations?

    Navigation was multiple DGPS [differential global positioning systems] coupled up with 2 very precise DR [dead-reckoning] 3-axis accelerometers, all integrated in WinFrog (proprietary software from Thales Geosolutions <http://www.thales-geopacific.com/offshore/index.html>). The best functional test we did was crossties, which suggested that average navigational errors were on the order of 1 meter, with (rare) maximum errors being about 3 meters. (A.J. Stevenson, written communtication, October 2001)

  3. How accurate are the heights or depths?

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

    Data values are missing in and around shallow or emergent features (islands) and where adjoining trackline coverage was not overlapping.

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

    Not applicable for raster data.


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: Data not to be used for navigational purposes.

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

    United States Geological Survey (USGS)
    c/o Florence L. Wong
    Geologist, GIS Coordinator
    USGS, MailStop 999, 345 Middlefield Road
    Menlo Park, CA 94025-3561
    USA

    (650) 329-5327 (voice)
    (650) 329-5190 (FAX)
    fwong@usgs.gov

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

  3. What legal disclaimers am I supposed to read?

    Please recognize the U.S. Geological Survey (USGS) as the source of this information.

    Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data.

    The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of this data, software, or related materials.

  4. How can I download or order the data?


Who wrote the metadata?

Dates:
Last modified: 10-Dec-2002
Last Reviewed: 2002
Metadata author:
United States Geological Survey (USGS)
c/o Florence L. Wong
Geologist, GIS Coordinator
USGS, MailStop 999, 345 Middlefield Road
Menlo Park, CA 94025-3561
USA

(650) 329-5327 (voice)
(650) 329-5190 (FAX)
fwong@usgs.gov

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata ("CSDGM version 2") (FGDC-STD-001-1998)


Generated by mp version 2.8.6 on Mon Dec 05 14:34:33 2005