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NSIDC-0667

King George and Livingston Islands: Velocities and Digital Elevation Model, Version 1

The data contain the time series totals of SAR derived detrended surface velocities from Livingston Island, as well as GeoTiff files generated from intensity tracking of Synthetic Aperture Radar (SAR) imagery. The images include average annual velocity and ice thickness of King George Island, and average annual velocity, ice thickness, and a digital elevation model of Livingston Island.

Geographic Coverage

Parameter(s):
  • Glaciers/Ice Sheets > Glacier Elevation/Ice Sheet Elevation
  • Glaciers/Ice Sheets > Glacier Thickness/Ice Sheet Thickness > Ice Thickness
  • Snow/Ice > Ice Velocity
Spatial Coverage:
  • N: -62.75, S: -62.75, E: -61, W: -61

  • N: -61.75, S: -61.75, E: -57.5, W: -57.5

Spatial Resolution:
  • Varies
Temporal Coverage:
  • 20 October 2007 to 18 March 2012
Temporal Resolution: Not specified
Data Format(s):
  • GeoTIFF
  • Microsoft Excel
Platform(s) ALOS
Sensor(s): PALSAR
Version: V1
Data Contributor(s): Batuhan Osmanoglu, Regine Hock
Please contact the data provider for the correct Data Citation for this data set.

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Detailed Data Description

The data contain the time series totals of SAR derived detrended surface velocities from Livingston Island, as well as GeoTiff files generated  from intensity tracking of Synthetic Aperture Radar (SAR) imagery.  The images include average annual velocity and ice thickness of King George Island, and average annual velocity, ice thickness, and a digital elevation model of Livingston Island.

Format

The data are in Microsoft Excel (.xls) and GeoTiff (.tif) formats.

File and Directory Structure

Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/DATASETS/AGDC/nsidc0667_hock directory. Within this directory, there are six files. See Table 1 for file names and descriptions.

Table 1. File and Descriptions

File Name Description
King_George_Island_average_annual_velocity.tif Mean surface ice velocity (m/yr) of the ice cap on King George Island, Antarctica, over the period January 2008 to January 2011. Refer to Osmanoglu, et al. (2013) Figure 5a.
King_George_Island_ice_thickness.tif Ice thickness (m/yr) of the ice cap on King George Island, Antarctica, calculated as a function of surface velocity according to Rignot et al. (1996). Refer to Osmanoglu, et al. (2013) Figure 5b.
Livingston_average_annual_velocity.tif Mean surface ice velocity (m/yr) of the ice cap on Livingston Island, Antarctica, over the period October 2007 to March 2011. Refer to Osmanoglu, et al. (2014) Figure 6a.
Livingston_ice_thickness.tif Ice thickness (m/yr) of the ice cap on Livingston Island, Antarctica, calculated as a function surface velocity according to Rignot et al. (1996). Refer to Osmanoglu, et al. (2014) Figure 6b.
Livingston_combined_dem.tif Digital elevation model (m asl) of the ice cap on Livingston Island, Antarctica, derived from merging elevation data derived from various sources. Refer to Osmanoglu, et al. (2014) Figure 3.
Livingston_velocity_timeseries_at_flux_gates.xls This file contains SAR derived detrended surface velocities (m/yr) and estimated errors averaged over each flux gate of 24 individual tidewater glaciers draining the Livingston Island ice cap. Data are available for 24 periods from October 2007 to January 2011. The file contains 24 data sheets, one for each flux gate in the order of the flux gate numbers given in Osmanoglu et al. (2014). See Figure 1 for a map of the flux gates. Refer to Figure 2 for graphs of the 24 velocities (Figure 7 in Osmanoglu et al. 2014).

Table 2. File Description

Column Description
Date 1 (MM/DD/YY) First satellite image acquisition date
Date 2 (MM/DD/YY) Second satellite image acquisition date
Mean velocity (m/yr) Derived through feature tracking the two SAR images
Velocity error (m/yr) Errors in derived surface velocities from feature tracking of PALSAR-1 images

Flux Gate Locations
Figure 1. Flux Gate Locations
Velocities
Figure 2. SAR-derived Velocities

File Size

The size of the .tif files range from 6.6 MB to 11 MB.  The Excel file is 98 KB.

Volume

Volume of the data set is approximately 47 MB.

Spatial Coverage

Livingston Island's coordinates are 62.75° S and 61.0° W. King George Island is located at 61.75° S and 57.5° W.

Spatial Resolution

The data for Livingston Island have a spatial resolution of 10 m grid spacing, and King George Island's spatial resolution is 50 m.

Temporal Coverage

Data were acquired from 20 October 2007 through 18 March 2012.

Parameter or Variable

The data's parameters are ice sheeet elevation, ice thickness, and ice velocity.

Software and Tools

Software and Tools

To view the .tif files, use any GeoTiff viewer software or double-click on the file from the ftp directory.  For the .xls file, use Microsoft Excel.

Data Acquisition and Processing

Data Acquisition & Processing

Data Acquisition

Synthetic aperture radar (SAR) data were used to derive surface ice velocities and to compile a new DEM for the Livingston Island ice cap. Data from two sources were included: (1) time series from the PALSAR-1 imaging system on board the Japanese Advanced Land Observing Satellite (ALOS-1) satellite (Rosenqvist et al., 2007) and (2) a bistatic image pair from the TerraSAR-X and TanDEM-X satellite mission (Krieger et al., 2007; Mittermayer et al., 2008).

PALSAR-1 provides L-band (1270 MHz) signals and was operational during 2006–2011. We used two parallel tracks (124 and 125) covering the entire ice cap, which provided a total of 25 images between October 2007 and March 2011. All images were collected in fine-beam single polarization mode. The bistatic TanDEM-X pair was acquired by TerraSAR-X and TanDEM-X satellites simultaneously, generating high quality interferometric data by removing the effects of temporal decorrelation.

Processing Steps

For the velocity data, GAMMA software was used to focus the ALOS PALSAR L1.0 data. An intensity tracking method within the GAMMA software obtained azimuth and range surface velocity estimates per pair to further process the scenes. Later, these data were combined and filtered to reduce noise and improve measurement accuracy. See Osmanoglu, et al. (2013) and Osmanoglue et al.(2014) for further detailed descriptions.

Error Sources

In the .tif files, there are data gaps in some regions.

Sensor or Instrument Description

On board Japan's Advanced Land Observing Satellite (ALOS) satellite, the PALSAR instrument provides enhanced sensor characteristics, including full polarimetry, variable off-nadir viewing, and ScanSAR operations, as well as significantly improved radiometric and geometric performance.

The TanDEM-X (TerraSAR-X add-on for digital elevation measurements) is a spaceborne radar interferometer that is based on two TerraSAR-X radar satellites flying in close formation. The primary objective of the TanDEM-X mission is the generation of a consistent global digital elevation model (DEM). 

References and Related Publications

Contacts and Acknowledgments

Dr. Batuhan Osmanoglu
Universities Space Research Association
NASA/GSFC
Mail code 618
Greenbelt, MD 20771 USA

Dr. Regine Hock
Geophysical Institute
University of Alaska
903 Koyukuk Dr.
Fairbanks, AK99775-7320 USA

Acknowledgments: 

This research was supported by NSF Division of Polar Programs (PLR) Grant Numbers 1043649.

Document Information

DOCUMENT CREATION DATE

08 February 2016

DOCUMENT REVISION DATE

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