Identification_Information:
  Citation:
    Citation_Information:
      Originator: B.K. Lucchitta
      Originator: J.M. Barrett
      Originator: J.A. Bowell
      Originator: J.G. Ferrigno
      Originator: K.F. Mullins
      Originator: C.E. Rosanova
      Originator: R.S. Williams, Jr.
      Publication_Date: 1995
      Title:
        Velocities of outlet glaciers, ice streams, and ice
        shelves, Antarctica, from satellite images
      Publication_Information:
        Publication_Place: Flagstaff, Arizona
        Publisher: U.S. Geological Survey
      Other_Citation_Details:
        Data contained in this data set are background information
        supporting the following publications.  Refer to data set
        documentation to determine which publication should be
        cited for when referring to an element of this data set.

        Ferrigno, J.G., Lucchitta, B.K., Mullins, K.F., Allison,
        A.L., Allen, R.J., and Gould, W.G., 1993, Velocity
        measurements and changes in position of Thwaites Glacier
        Ice Berg Tongue from aerial photographs, Landsat images,
        and NOAA AVHRR data: Annals of Glaciology, v.17, p. 239-
        244.

        Lucchitta, B.K., Mullins, K.F., Allison, A.L., and
        Ferrigno, J.G., 1993, Antarctic glacial tongue velocities
        from Landsat images: First results: Annals of Glaciology,
        v. 17, p. 356-366.

        Lucchitta, B.K., Smith, C.E., Bowell, J.A., and Mullins,
        K.F., 1994, Velocities and mass balance of Pine Island
        Glacier, West Antarctica, Derived from ERS-1 SAR images:
        Proceedings, 2nd ERS-1 Symposium, Hamburg, Germany, 11-14
        Oct. 1993, ESA SP-361, p. 147-151.

        Lucchitta, B.K., Mullins, K.F., Smith, C.E., and Ferrigno,
        J.G., in press, Velocities of Smith Glacier Ice Tongue and
        Dotson Ice Shelf, Walgreen Coast, Marie Byrd Land, West
        Antarctica: Annals of Glaciology, v. 20.

        Lucchitta, B.K., Smith, C.E., and Mullins, K.F.,
        Velocities and mass balance of Pine Island Glacier, West
        Antarctica: Submitted to Annals of Glaciology.
      Online_Linkage: <URL:http://geochange.er.usgs.gov/pub/antarctica/glacier-velocity/Core/meta/report.html>
  Description:
    Abstract:
      This report summarizes the results of velocity measurements of
      outlet glaciers, ice streams, and ice shelves around the
      Antarctic periphery.  For some regions, where suitable images
      were available, the same area was measured repeatedly to
      validate the data or register changes in velocity with time.
      The results given here are a compendium of published papers
      and work in progress.  The results constitute a data base that
      will be added to and amended as more velocity measurements
      become available.
    Purpose:
      Changes in global climate and sea level are intricately linked
      to changes in the area and volume of polar ice sheets.  Thus,
      melting of the ice sheets may severely impact the densely
      populated coastal regions on Earth.  Melting of the West
      Antarctic ice sheet alone could raise sea level by
      approximately 5 m.  In spite of their importance, the current
      mass balances (the net gains or losses) of the Antarctic ice
      sheets are not known.  Because of difficult logistic problems
      in Antarctica, field research has focused on only a few major
      ice streams and outlet glaciers.  Yet, to understand the ice
      sheet dynamics fully, we must carefully document all of the
      coastal changes associated with advance and retreat of ice
      shelves, outlet glaciers, and ice streams.

      A critical parameter of ice sheets is their velocity field,
      which, together with ice thickness, allows the determination
      of discharge rates.  Remote sensing, using moderate- to high-
      resolution satellite images, permits glacier movement to be
      measured on sequential images covering the same area; the
      velocities can be measured quickly and relatively
      inexpensively by tracking crevasses or other patterns that
      move with the ice.  Especially important are velocities where
      the ice crosses the glaciers grounding lines (locations along
      the coast where the ice is no longer ground supported and
      begins to float).
  Time_Period_of_Content:
    Time_Period_Information:
      Range_of_Dates/Times:
        Beginning_Date: 1972
        Ending_Date: 19921204
    Currentness_Reference:
      Range specified indicates date of earliest image used and date
      of latest image used.
  Status:
    Progress: Complete
    Maintenance_and_Update_Frequency: As needed
  Spatial_Domain:
    Bounding_Coordinates:
      West_Bounding_Coordinate: -142.0
      East_Bounding_Coordinate: 130.0
      North_Bounding_Coordinate: -67.0
      South_Bounding_Coordinate: -76.0
  Keywords:
    Theme:
      Theme_Keyword_Thesaurus: None
      Theme_Keyword: Glacier
      Theme_Keyword: Glacier tongues
      Theme_Keyword: Glacier velocity
    Place:
      Place_Keyword_Thesaurus: None
      Place_Keyword: Antarctica
  Access_Constraints: none
  Use_Constraints: none
  Point_of_Contact:
    Contact_Information:
      Contact_Person_Primary:
        Contact_Person: Baerbel K. Lucchitta
        Contact_Organization: Branch of Astrogeology
      Contact_Address:
        Address_Type: mailing address
        Address:
          Mail Stop 9580
          U.S. Geological Survey
          2255 N. Gemini Drive
        City: Flagstaff
        State_or_Province: AZ
        Postal_Code: 86001-1689
        Country: USA
      Contact_Voice_Telephone: (520) 556-7176
      Contact_Facsimile_Telephone: (520) 556-7014
      Contact_Electronic_Mail_Address: blucchitta@iflag2.wr.usgs.gov

Data_Quality_Information:
  Attribute_Accuracy:
    Attribute_Accuracy_Report:
      We use two methods to determine the glacial velocities:  an
      interactive one in which we visually trace crevasse patterns
      (Lucchitta and others, 1993) and an autocorrelation program
      developed by Bindschadler and Scambos (1991) and Scambos and
      others (1992).  First, we digitally co-register the images by
      using a minimum of three well-dispersed fixed points (such as
      nunataks or ice walls) to calculate a least-squares fit to a
      first-order polynomial equation.  This insures that only a
      rotational/translational correction is made and no new
      internal error is introduced during the geometric resampling.
      In the interactive technique, we then match and align the
      crevasse patterns displaced with time, and record the starting/
      ending image coordinates for each point.  To obtain the
      distribution of average velocities over the length of the
      glacier tongues, we also use the distance from the location of
      each point on the earlier image to a base line drawn
      perpendicular to glacier movement and ideally lying on the
      grounding line; where the grounding line is complex, the base
      line may only approximate its position. Next, a digitized file
      is made, tracing the glacier ice movements and defining the
      glacier's baseline (or grounding line).  This file is used to
      calculate the velocity and distance statistics by measuring
      the displacements along the curve that approximates the ices
      movement per given time interval.  For each measured point, a
      displacement vector is plotted on the image, commonly the
      earlier one of the pair, to illustrate the relative velocities
      between glaciers and time intervals.
  Logical_Consistency_Report:
    Because the velocity field may also change across the glacier
    tongues, we divide the wider glaciers into several longitudinal
    paths.  Next we obtain an estimate of the spread of measured
    points by performing a regression analysis on the data.  This
    includes an option to cull bad data points by inputting a variable
    for the standard deviation.  If used, the mean absolute deviation
    of the points about this line is calculated and any points lying
    outside that distance are disregarded during the statistical
    analysis.  Calculations are made for the entire glacier as well as
    for each individual path.  The 95% confidence interval for the
    regression coefficient is calculated along with the correlation
    coefficient.
  Completeness_Report:
    The files contained in this data base are the output ASCII files
    generated by this statistical software.  Each file identifies the
    images used, their dates, and resolutions, the time interval
    between image acquisitions and the statistical variables used to
    make the calculations. These data are followed by a table of the
    distance and velocity values for each point and the statistics
    calculated per path. The measurement results are shown in graphs
    that display average velocities per given time interval versus the
    distance from the base line for all points in each field (not
    included in this data base).

    In the auto-correlation method we use the same techniques for
    coregistration and graphic and statistical display.  However, we
    may not divide the glaciers into segments and paths, but instead
    combine all velocities and show variations across the glacier by
    color contours (also not shown in this report).
  Positional_Accuracy:
    Horizontal_Positional_Accuracy:
      Horizontal_Positional_Accuracy_Report:
        Accuracy of point positions is limited by the digital
        representation of the images.  The accuracy with which
        individual features of the ice tongues are correlated
        (from image to image) cannot be assessed, because it is
        confounded with the spatial variation of the velocity
        field.
  Lineage:
    Source_Information:
      Source_Citation:
        Citation_Information:
          Originator: Ferrigno, J.G.
          Originator: Lucchitta, B.K.
          Originator: Mullins, K.F.
          Originator: Allison, A.L.
          Originator: Allen, R.J.
          Originator: Gould, W.G.
          Publication_Date: 1993
          Title:
            Velocity measurements and changes in position of
            Thwaites Glacier Ice Berg Tongue from aerial
            photographs, Landsat images, and NOAA AVHRR data
          Series_Information:
            Series_Name: Annals of Glaciology
            Issue_Identification: v.17, p. 239-244
      Type_of_Source_Media: paper
      Source_Time_Period_of_Content:
        Time_Period_Information:
          Single_Date/Time:
            Calendar_Date: 1993
        Source_Currentness_Reference: publication date
      Source_Citation_Abbreviation: Ferrigno et al., 1993
      Source_Contribution: Velocity of Thwaites Glacier tongue

    Source_Information:
      Source_Citation:
        Citation_Information:
          Originator: Lucchitta, B.K.
          Originator: Mullins, K.F.
          Originator: Allison, A.L.
          Originator: Ferrigno, J.G.
          Publication_Date: 1993
          Title:
            Antarctic glacial tongue velocities from Landsat
            images: First results
          Series_Information:
            Series_Name: Annals of Glaciology
            Issue_Identification: v. 17, p. 356-366
      Type_of_Source_Media: paper
      Source_Time_Period_of_Content:
        Time_Period_Information:
          Single_Date/Time:
            Calendar_Date: 1993
        Source_Currentness_Reference: publication date
      Source_Citation_Abbreviation: Lucchitta et al., 1993
      Source_Contribution:
        Velocities of Stancomb-Wills, Berg, Thwaites, Land,
        Drygalski, Kaya, and Riiser-Larsen glacier tongues.

    Source_Information:
      Source_Citation:
        Citation_Information:
          Originator: Lucchitta, B.K.
          Originator: Smith, C.E.
          Originator: Bowell, J.A.
          Originator: Mullins, K.F.
          Publication_Date: 1994
          Title:
            Velocities and mass balance of Pine Island
            Glacier, West Antarctica, Derived from ERS-1 SAR
            images
          Series_Information:
            Series_Name: ESA SP
            Issue_Identification: 361, p. 147-151
          Other_Citation_Details:
            Proceedings, 2nd ERS-1 Symposium, Hamburg,
            Germany, 11-14 Oct. 1993
      Type_of_Source_Media: paper
      Source_Time_Period_of_Content:
        Time_Period_Information:
          Single_Date/Time:
            Calendar_Date: 1994
        Source_Currentness_Reference: publication date
      Source_Citation_Abbreviation: Lucchitta et al., 1994a
      Source_Contribution: Velocity of Pine Island Glacier

    Source_Information:
      Source_Citation:
        Citation_Information:
          Originator: Lucchitta, B.K.
          Originator: Mullins, K.F.
          Originator: Smith, C.E.
          Originator: Ferrigno, J.G.
          Publication_Date: 1994
          Title:
            Velocities of Smith Glacier Ice Tongue and Dotson
            Ice Shelf, Walgreen Coast, Marie Byrd Land, West
            Antarctica
          Series_Information:
            Series_Name: Annals of Glaciology
            Issue_Identification: v. 20, p. 101-109
      Type_of_Source_Media: paper
      Source_Time_Period_of_Content:
        Time_Period_Information:
          Single_Date/Time:
            Calendar_Date: 1994
        Source_Currentness_Reference: publication date
      Source_Citation_Abbreviation: Lucchitta et al., 1994b
      Source_Contribution:
        Velocity of Smith glacier ice tongue and Dotson Ice Shelf

    Source_Information:
      Source_Citation:
        Citation_Information:
          Originator: Lucchitta, B.K.
          Originator: Smith, C.E.
          Originator: Mullins, K.F.
          Publication_Date: 1995
          Title:
            Velocities and mass balance of Pine Island
            Glacier, West Antarctica
          Series_Information:
            Series_Name: Annals of Glaciology
            Issue_Identification: v. 21
          Other_Citation_Details: in press
      Type_of_Source_Media: paper
      Source_Time_Period_of_Content:
        Time_Period_Information:
          Single_Date/Time:
            Calendar_Date: 1995
        Source_Currentness_Reference: publication date
      Source_Citation_Abbreviation: Lucchitta et al., 1995
      Source_Contribution: Velocity of Pine Island glacier

    Process_Step:
      Process_Description:
        For Landsat images, we obtain either computer-compatible
        tapes (CCTs) of MSS images, or, where tapes are
        nonexistent, the lowest generation transparency available
        for band 7 (near-infrared).   These transparencies are
        third- and fourth-generation negatives, which have lost
        some image detail through the duplication process.  We use
        only photographic products for TM images because of the
        high cost of CCTs.  For TM images acquired before 1989 we
        obtain fourth-generation negatives of band 4 (near-
        infrared), and for images acquired after 1989 we use third-
        generation color negatives (only color photographic
        products are now available from the vending company).  The
        quality of some of these images is poor, as they are not
        especially processed for the high reflectivity of snow and
        ice.  The transparencies are scanned at 50 micron to
        obtain a digital data set.  The ground resolution of the
        scanned images varies, depending on the size of the
        original transparency.  To obtain the ground resolution
        per pixel, the nominal Landsat image height on the ground,
        in km, is scaled to the actual image height of the scanned
        images.

        We generally register Landsat 1, 2, and 3 images to
        Landsat 4 and 5 images, because the latter have more
        stable internal geometry and higher resolution than the
        earlier images.  Several tests were made to compare the
        internal geometry of 3rd and 4th generations negatives
        with the original digital data.  All of these tests, as
        well as several made between original and scanned images
        of transparencies, showed an insignificant degree of
        geometric error between products.  These tests demonstrate
        that geometrical errors within the transparencies will
        contribute little to statistical variance between
        measurements.  Loss of resolution and misidentification of
        features play a more important role in measurement error
        made with these images. Borgeson and others (1985) found
        that Landsat 5 images are accurate to about 0.4 pixels,
        meeting national Horizontal Map Accuracy standards for
        scales of 1:100,000 and smaller, and that Landsat 4 images
        are accurate to 0.8 pixel levels.  Welch and others (1985)
        reported that Landsat 4 and 5 images meet accuracy
        standards for maps of 1:50,000 scale or smaller and are
        well suited to maps of 1:100,000 scale.
      Source_Used_Citation_Abbreviation: LANDSAT
      Process_Date: 1994
      Source_Produced_Citation_Abbreviation: Ferrigno et al., 1993
      Source_Produced_Citation_Abbreviation: Lucchitta et al., 1993
      Source_Produced_Citation_Abbreviation: Lucchitta et al., 1994a
      Source_Produced_Citation_Abbreviation: Lucchitta et al., 1994b

    Process_Step:
      Process_Description:
        For ERS images, we obtain CCTs of the geocoded version
        (placed in Universal Polar Stereographic projection using
        the WGS 1984 ellipsoid).  The pixel size is 12.5 m on the
        ground (resolution approximately 30m).  The images are
        coregistered by either (1) matching fixed points such as
        nunataks (land masses projecting through the ice), or (2)
        using the furnished coordinates based on orbital
        parameters.  We obtained the same results by both methods,
        increasing our confidence in the accuracy of the nominal
        image location, which is supposed to be less than 50 m
        (Roth and others, in press).  For a more detailed error
        evaluation for Landsat images see Lucchitta and others
        (1993 and 1994), and for ERS-1 images see Lucchitta
        and others (1994 and 1995).
      Process_Date: 1994
      Source_Used_Citation_Abbreviation: ERS-1
      Source_Produced_Citation_Abbreviation: Lucchitta et al., 1995

Spatial_Data_Organization_Information:
  Indirect_Spatial_Reference:
    Point locations contained in the data files are not georeferenced
    although in principle they could be if the corners of the images
    from which they were digitized were georeferenced.

Spatial_Reference_Information:
  Horizontal_Coordinate_System_Definition:
    Local:
      Local_Description:
        We generally register Landsat 1, 2, and 3 images to
        Landsat 4 and 5 images, because the latter have more
        stable internal geometry and higher resolution than the
        earlier images.

        We digitally co-register the images by using a minimum of
        three well-dispersed fixed points (such as nunataks or ice
        walls) to calculate a least-squares fit to a first-order
        polynomial equation.  This insures that only a rotational/
        translational correction is made and no new internal error
        is introduced during the geometric resampling.  In the
        interactive technique, we then match and align the
        crevasse patterns displaced with time, and record the
        starting/ending image coordinates for each point.  To
        obtain the distribution of average velocities over the
        length of the glacier tongues, we also use the distance
        from the location of each point on the earlier image to a
        base line drawn perpendicular to glacier movement and
        ideally lying on the grounding line; where the grounding
        line is complex, the base line may only approximate its
        position. Next, a digitized file is made, tracing the
        glacier ice movements and defining the glacier's baseline (
        or grounding line).  This file is used to calculate the
        velocity and distance statistics by measuring the
        displacements along the curve that approximates the ices
        movement per given time interval.  For each measured
        point, a displacement vector is plotted on the image,
        commonly the earlier one of the pair, to illustrate the
        relative velocities between glaciers and time intervals.
      Local_Georeference_Information:
        Although in principle the images could be registered to
        the earth's surface, for this exercise georeference is
        not necessary, since the objective is merely to understand
        ice movement through time and among paths within a glacier
        tongue.  Hence the data are not explicitly georeferenced.

Entity_and_Attribute_Information:
  Overview_Description:
    Entity_and_Attribute_Overview:
      The velocity files are grouped within folders by name of
      glacier or shelf and by year of the two image pairs used in
      the calculations.  For example: in the landsat/thwaites
      directory the file th7384.dst contains the velocity data for
      the 1973/1984 image pair covering the Thwaites glacier
      region.  For each pair, the following information is given:
      (1) the displacement per given time interval for each point of
      a path, segment, or the entire glacier, (2) the velocities per
      year for the same points, (3) statistical parameters of
      individual paths, segments, or entire glaciers, including
      standard deviations, and (4) distance to grounding line for
      each point.
    Entity_and_Attribute_Detail_Citation: Lucchitta et al., 1993

Distribution_Information:
  Distributor:
    Contact_Information:
      Contact_Person_Primary:
        Contact_Person: Peter N. Schweitzer
      Contact_Address:
        Address_Type: mailing address
        Address:
          Mail Stop 955 National Center
          U.S. Geological Survey
          12201 Sunrise Valley Drive
        City: Reston
        State_or_Province: VA
        Postal_Code: 22092
        Country: USA
      Contact_Voice_Telephone: (703) 648-6533
      Contact_Facsimile_Telephone: (703) 648-6647
      Contact_Electronic_Mail_Address: pschweitzer@usgs.gov

  Distribution_Liability:
    This report is preliminary and has not been reviewed for
    conformity with U.S. Geological Survey editorial standards (or
    with the North American Stratigraphic Code).  Any use of trade,
    product, or firm names is for descriptive purposes only and does
    not imply endorsement by the U.S. Government.

  Standard_Order_Process:
    Digital_Form:
      Digital_Transfer_Information:
        Format_Name: TEXT
        Format_Information_Content: Glacier-velocity data
      Digital_Transfer_Option:
        Online_Option:
          Computer_Contact_Information:
            Network_Address:
              Network_Resource_Name: <URL:ftp://geochange.er.usgs.gov/pub/antarctica/glacier-velocity/>
              Network_Resource_Name: <URL:http://geochange.er.usgs.gov/pub/antarctica/glacier-velocity/Core/meta/report.html>
          Online_Computer_and_Operating_System:
            Data General AViiON 6220 system running DG/UX
            version 5.4R3.10 (UNIX)
    Fees: none

Metadata_Reference_Information:
  Metadata_Date: 19960207
  Metadata_Contact:
    Contact_Information:
      Contact_Person_Primary:
        Contact_Person: Peter N. Schweitzer
      Contact_Address:
        Address_Type: mailing address
        Address:
          Mail Stop 955
          U.S. Geological Survey
          12201 Sunrise Valley Drive
        City: Reston
        State_or_Province: VA
        Postal_Code: 22092
        Country: USA
      Contact_Voice_Telephone: (703) 648-6533
      Contact_Facsimile_Telephone: (703) 648-6647
      Contact_Electronic_Mail_Address: pschweitzer@usgs.gov
  Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
  Metadata_Standard_Version: 19940608
