MEaSUREs InSAR-Based Antarctica Ice Velocity Map

Summary

This data set (NSIDC-0484), part of the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) Program, provides the first comprehensive, high-resolution, digital mosaics of ice motion in Antarctica assembled from multiple satellite interferometric synthetic-aperture radar data. Data were acquired during the International Polar Year 2007 to 2009.

These maps were built from spring 2009 data from the Canadian Space Agency (CSA)'s and MacDonald, Dettwiler and Associates Ltd. (MDA)'s RADARSAT-2, spring 2007-2008-2009 data from European Space Agency (ESA)'s Envisat Advanced Synthetic Aperture Radar (ASAR), and fall 2007-2008 data from the Japan Aerospace Exploration Agency (JAXA)'s Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR), complemented by patches of CSA's RADARSAT-1 data from fall 2000 and ESA's Earth Remote Sensing Satellites ERS-1 and -2 data from spring 1996. Each radar instrument contributes its unique coverage and performance level. The final mosaics assemble 900 satellite tracks and more than 3,000 orbits of radar data. Data acquisitions between 2006 and 2011 are courtesy of the IPY Space Task Group.

Data are available via FTP at 450 m and 900 m spacings, in both binary format (.dat) with an ENVI text header (.txt) and NetCDF.

Note. These data are considered provisional pending a review by the MEaSUREs program. Once the data have been reviewed, this statement will be removed from this documentation.

Citing These Data

Literature Citation

We kindly request that you acknowledge the use of this data set by referencing the following peer-reviewed publication:

Rignot, E., J. Mouginot, and B. Scheuchl. 2011. Ice Flow of the Antarctic Ice Sheet, Science, Vol. 333(6048): 1427-1430. doi 10.1126/science.1208336.

Data Citation

We kindly request that you cite the use of this data set in a publication using the following citation example. For more information, see our Use and Copyright Web page.

Rignot, E., J. Mouginot, and B. Scheuchl. 2011. MEaSUREs InSAR-Based Antarctica Ice Velocity Map [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center. doi:10.5067/MEASURES/CRYOSPHERE/nsidc-0484.001

Overview Table

Category Description
Data format Binary with ENVI text header
NetCDF
Spatial coverage Southernmost Latitude: 90°S
Northernmost Latitude: 60°S
Westernmost Longitude: 180°W
Easternmost Longitude: 180°E
Spatial resolution 450 m
900 m
Temporal coverage and resolution Data were collected between 1996 and 2011.
Projection description Polar stereographic with true scale at 71° south
File naming convention antarctica_ice_velocity_[450m/900m].dat
antarctica_ice_velocity_[450m/900m].nc
File size 1300 MB (450 m)
300 MB (900 m)
Parameters Ice velocity (vx, vy)
Error
Procedures for obtaining data Data are available via FTP.

Table of Contents

  1. Contacts and Acknowledgments
  2. Detailed Data Description
  3. Data Access and Tools
  4. Data Acquisition and Processing
  5. References and Related Publications
  6. Document Information

1. Contacts and Acknowledgments

Investigators

Dr. Eric Rignot
University of California, Irvine
Department of Earth System Science
Croul Hall
Irvine, California 92697
USA

Dr. Jeremie Mouginot
University of California, Irvine
Department of Earth System Science
Croul Hall
Irvine, California 92697
USA

Dr. Bernd Scheuchl
University of California, Irvine
Department of Earth System Science
Croul Hall
Irvine, California 92697
USA

Technical Contact

NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449  USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org

Acknowledgements

These data were generated through a grant from the NASA MEaSUREs program.

Spaceborne Synthetic Aperture Radar (SAR) acquisitions were provided through the following data grants:

  • ALOS PALSAR: Japan Aerospace Exploration Agency (JAXA)
  • ENVISAT ASAR, ERS-1, ERS-2: European Space Agency (ESA)
  • RADARSAT-1, RADARSAT-2: Canadian Space Agency (CSA)

Data acquisitions between 2006 and 2011 are courtesy of the International Polar Year (IPY) Space Task Group.

2. Detailed Data Description

Sample Image

Sample Image
Figure 1. Antarctic ice velocity derived from ALOS PALSAR, Envisat ASAR, RADARSAT- 2
and ERS-1/2 satellite radar interferometry color coded on a logarithmic scale.
(Rignot, Mouginot, and Scheuchl 2011)

Format

These data are available in the following formats:

  • Binary file with ENVI text header
  • NetCDF

File and Directory Structure

Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/DATASETS/nsidc0484_MEASURES_antarc_vel_V01/ directory. The 00README.txt file in this directory contains additional information about the data set. Data files are stored by spatial resolution in the /450m/ and /900m/ subfolders. Each folder contains the data files listed in Table 2, where [450m/900m] denotes the corresponding spatial resolution.

Example file names:

  • .../450m/antarctica_ice_velocity_450m.dat
  • .../900m/antarctica_ice_velocity_900m.dat

Table 2. File and Directory Description
File Description

antarctica_ice_velocity_[450m/900m].dat

Velocity, binary file (big endian)

antarctica_ice_velocity_[450m/900m]_error.dat

Error estimate, binary file (big endian)

antarctica_ice_velocity_[450m/900m].hdr
antarctica_ice_velocity_[450m/900m]_error.hdr

Header files for reading .dat files into ENVI

antarctica_ice_velocity_[450m/900m].nc

Velocity, NetCDF format

antarctica_ice_velocity_[450m/900m]_info.txt

ASCII text file with projection information

File Size

Files range from approximately 350 MB to 1.4 GB.

Spatial Coverage

The data set spans the continent of Antarctica.

Southernmost Latitude: 90°S
Northernmost Latitude: 60°S
Westernmost Longitude: 180°W
Easternmost Longitude: 180°E

Spatial Coverage Map

spatial coverage map
Figure 2. Antarctic ice velocity derived from (A) PALSAR, (B) ASAR, (C) RADARSAT-2, and (D) RADARSAT-1 and ERS-1 and 2 satellite
radar interferometry color coded on a logarithmic scale and overlaid on a MODIS mosaic of Antarctica. Projection is polar stereographic
at 71°S secant plane. Thick black lines delineate major ice divides.
(Rignot, Mouginot, and Scheuchl 2011)

Spatial Resolution

The velocity maps are provided at 450 m and 900 m spacings.

Projection

Polar stereographic with true scale at 71° S.

Temporal Coverage

The data used in this data set were collected between 1996 and 2011. Detailed information is provided in Section 4: Data Acquisition and Processing.

Parameter or Variable

These maps provide velocity data for the Antarctic Ice Sheet at 450 m and 900 m spacings. Each data point contains velocity information (meters per year) in the x and y direction as defined by the polar stereographic grid (vx and vy respectively). Error estimates for the velocity magnitude are also provided, however, these values should be used more as an indication of relative quality rather than absolute error. More information about the error estimates is provided in the Quality Assessment section as well as in Rignot, et al. 2011.

Parameter Description

Table 3. Variable Description
Variable Description
vx Velocity in m/year in x direction
vy Velocity in m/year in y direction
err Estimated error in velocity magnitude


Quality Assessment

A detailed description of these data and their quality is provided in Rignot, et al., 2011. The precision of ice flow mapping varies with the sensor, the geographic location, the technique of interferometric analysis (see Section 4 for details), the time period of analysis, the repeat cycle, and the amount of data stacking. The error estimates are summarized in Table 4. The error map in Figure 3 takes into account the following error sources:

  • Error of speckle tracking and interferometric phase analysis respectively
  • Errors caused by ionospheric perturbations (strongest in the azimuth direction, stronger in L-band compared to C-band, stronger in the East Antarctic Ice Sheet (EAIS) compared to the West Antarctic Ice Sheet (WAIS) because ionospheric perturbations are more abundant near the magnetic pole
  • Data stacking (reduces the error noise as the square root of the number of interferometric pairs averaged)
  • Respective weight of each instrument in the mosaicking

The total error is the square root of the sum of the independent errors squared. More details on the error estimates are provided in Rignot, et al., 2011 (supplementary online material). Table 4 provides the error in ice velocity mapping for each sensor, without data stacking, in range (Rg) and azimuth (Az).

Table 4. Error in Ice Velocity Mapping (m/yr)
Sensor Repeat Cycle
(day)
Pixel Size Speckle Tracking PhaseRg
(m/yr)
IonosphereAz
(m/yr)
Total Error
(m/yr)
Rg (m) Az (m) Rg (m/yr) Az (m/yr)
ALOS (WAIS) 46 4.7 3.3 0.5 0.2 0.03 17 17
ALOS (EAIS) 46 4.7 3.3 0.5 0.2 0.03 8 8
ASAR 35 4.7 3.3 1.6 0.3 0.03 4.1 4
RADARSAT-2 24 11.8 5.3 2.1 0.6 0.021 5.9 6
RADARSAT-1 24 8.1 5.3 2.4 0.6 0.03 5.9 6
ERS-1 and -2 1 7.9 4.0 56 12 0.73 N/A 1

 

 

error map
Figure 3. Velocity magnitude error on a linear scale color
coded from 1 to greater than 16 m/yr. Thick black lines
delineate major ice divides and the grounding line
(Rignot, et al. 2011).

3. Data Access and Tools

Data Access

Data are available via FTP. Registered users will receive e-mail notification about any product changes and new data availability. Please complete the User Registration Form to receive these notifications.

Volume

Data volume

450 m spacing: 2.8 GB
900 m spacing: 0.7 GB
Total volume: 3.5 GB

Software and Tools

Data are accessible using a variety of software.

Related Data Collections

4. Data Acquisition and Processing

Theory of Measurements

This data set provides ice velocity information for the entire Antarctic continent, derived from a variety of satellite radar interferometry data. Two techniques of interferometric analysis were used to generate the maps:

  1. Speckle tracking in both along (azimuth) and across (range) track directions
    Calculation of two dimensional offsets in amplitude imagery
  2. Combinations of (range) interferometric phases along two independent tracks
    Combination of interferometric phases of two independent tracks to retrieve the surface flow vector

In both cases, surface parallel flow is assumed, a conventional approach for ice sheets.

Data Acquisition Methods

Ice velocity information for the Antarctic Ice Sheet was derived using satellite synthetic aperture radar interferometry (InSAR) data from spring 2009 data from the Canadian Space Agency (CSA)'s and MacDonald, Dettwiler and Associates Ltd. (MDA)'s RADARSAT-2, spring 2007-2008-2009 data from European Space Agency (ESA)'s Envisat Advanced Synthetic Aperture Radar (ASAR), and fall 2007-2008 data from the Japan Aerospace Exploration Agency (JAXA)'s Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR), complemented by patches of CSA's RADARSAT-1 data from fall 2000 and ESA's Earth Remote Sensing Satellites ERS-1 and -2 data from spring 1996. Each radar instrument contributes its unique coverage and performance level. The final mosaics assemble 900 satellite tracks and more than 3,000 orbits of radar data. Data acquisitions between 2006 and 2011 were coordinated through the IPY Space Task Group.

The 450 m map contains some minor improvements compared with the 900 m product, such as slightly better coverage in West Antarctica due to the inclusion of a few additional tracks and a tide correction for Ross and Ronne ice shelves (RADARSAT-2, 2009 tracks only). The Theory of Measurements section of the MEaSUREs InSAR-Based Ice Velocity Maps of Central Antarctica: 1997 and 2009 documentation contains additional details about this correction.

Data Sources

Table 5 describes the data sources used in this data set.

Table 5. Temporal and spatial coverage of source satellite data
Platform Look Dir. Mode Repeat Cycle (day) Incidence Angle Resolution
Rg x Az (m)
Swath (km) Frequency (GHz) # of Proc. Tracks Raw Data Volume Year
ERS-1 & 2 Right N/A 1-3 23 13x4 83 5.33 60 0.5 1996
RADARSAT-1 Left S2-S7 24 28-47 12x5-17x6 62 5.33 72 0.5 1997
  Right various 24 18-38 7x5-12x5 62 5.33 84 0.5 2000
ENVISAT Right IS2 35 23 13x5 70 5.33 115/130/210 1/1/2 2007/2008/2009
RADARSAT-2 Left S5/EH4 24 41/57 12x5 70 5.33 135/14 4/1 2009/2011
ALOS PALSAR Right FBS 46 39 7x4 45 1.27 64/204/296 2/6/9 2006/2007/2008

 

5. References and Related Publications

Rignot, E., S. Jacobs, J. Mouginot, and B. Scheuchl. 2013. Ice Shelf Melting Around Antarctica. Science, 341(6143): 266-270. doi:10.1126/science.1235798

Rignot, E., J. Mouginot, and B. Scheuchl. 2011. Ice Flow of the Antarctic Ice Sheet. Science, 333(6048): 1427-1430. doi:10.1126/science.1208336.

Rignot, E., J. Mouginot, and B. Scheuchl. 2011. Antarctic grounding line mapping from differential satellite radar interferometry. Geophys. Res. Lett., 38, L10504, doi:10.1029/2011GL047109.

Rignot, E., J. L. Bamber, M. R. Van Den Broeke, C. Davis, Y. H. Li, W. J. Van De Berg, & E. Van Meijgaard. 2008. Recent Antarctic ice mass loss from radar interferometry and regional climate modelling. Nature Geoscience, 1(2), 106-110. doi:10.1038/ngeo102

Michel, R., and E. Rignot. 1999. Flow of Glacier Moreno, Argentina, from Repeat-Pass Shuttle Imaging Radar Images: Comparison of the Phase Correlation Method with Radar Interferometry. J. Glaciol. 45, 93100.

The following related documents are available

Table 6. Related Documents
Document Description URL
NASA MEaSUREs Data at NSIDC NSIDC MEaSUREs Data Web site http://nsidc.org/data/measures/index.html
NASA MEaSUREs NASA MEaSUREs Projects Web site http://earthdata.nasa.gov/our-community/community-data-system-programs/measures-projects


6. Document Information

Acronyms

The following acronyms are used in this document.

Table 7. Acronyms
Acronym Description

ALOS

Advanced Land Observing System

ASAR

Advanced Synthetic Aperture Radar

CSA

Canadian Space Agency

ERS

Earth Remote Sensing Satellite

ESA

European Space Agency

FTP

File Transfer Protocol

IPY

International Polar Year

JAXA

Japan Aerospace Exploration Agency

NASA

National Aeronautics and Space Administration

NSIDC

National Snow and Ice Data Center

PALSAR

Phased Array Type L-band Synthetic Aperture Radar

RADARSAT

Radar Satellite

SAR

Synthetic Aperture Radar

URL

Uniform Resource Locator


Document Creation Date

October 2011

Document Revision Date

September 2013

Document URL

http://nsidc.org/data/docs/measures/nsidc0484_rignot/index.html