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: 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. 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_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 918 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) 648-6560 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: Network_Resource_Name: 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 918 U.S. Geological Survey 12201 Sunrise Valley Drive City: Reston State_or_Province: VA Postal_Code: 20192 Country: USA Contact_Voice_Telephone: (703) 648-6533 Contact_Facsimile_Telephone: (703) 648-6560 Contact_Electronic_Mail_Address: pschweitzer@usgs.gov Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata Metadata_Standard_Version: 19940608