MEaSUREs InSAR-Based Antarctica Ice Velocity Map
Summary
This data set, part of the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) program, provides the first comprehensive, high-resolution, digital mosaic 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.
This map was 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 mosaic assembles 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 in a variety of formats: 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
The generation of this data set and its scientific interpretation are discussed in the following citation. We kindly request that you acknowledge the use of this data set by referencing the following citation:
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
These data are offered free of charge. You may use these data freely, provided that you cite NSIDC as the source, and provide an acknowledgment in any published papers.
The following examples show how to cite the use of these data sets in a publication. List the principal investigators, year of data set release, data set title and version number, dates of the data you used (for example, March to June 2004), publisher: NSIDC, and digital media.
Rignot, E., J. Mouginot, and B. Scheuchl. 2011. MEaSUREs InSAR-Based Antarctica Ice Velocity Map. Boulder, Colorado USA: NASA EOSDIS Distributed Active Archive Center at NSIDC. [list dates of data used]. http://nsidc.org/data/nsidc-0484.html
Overview Table
| Category | Description |
|---|---|
| Data format | The data are provided in the following formats: Binary file with ENVI text header NetCDF |
| Spatial coverage and resolution |
Southernmost Latitude: 90°S Northernmost Latitude: 60°S Westernmost Longitude: 180°W Easternmost Longitude: 180°E 900 m resolution |
| Temporal coverage and resolution | Data were collected between 1996 and 2011. |
| Projection description | The velocity map is provided in polar stereographic projection with true scale at 71° south |
| File naming convention | Antarctica_ice_velocity_binary.dat |
| File size | Files are approximately 300 MB. |
| Parameters | Ice velocity (vx and vy) Error |
| Procedures for obtaining data | Data are available via FTP. |
Table of Contents
- Contacts and Acknowledgments
- Detailed Data Description
- Data Access and Tools
- Data Acquisition and Processing
- References and Related Publications
- 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
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
The data are provided in the following formats:
1. Binary file with ENVI text header
2. 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. Within this directory, the data are provided in multiple formats, as listed below.
| File | Description |
|---|---|
Antarctica_ice_velocity_binary.dat |
Binary file (big endian) |
Antarctica ice_velocity_error.dat |
Binary file (big endian) for data error |
Antarctica_ice_velocity_binary.hdr |
ENVI header files for reading the corresponding .dat files into ENVI |
Antarctica_ice_velocity_info.txt |
ASCII text file containing projection information |
Antarctica_ice_velocity.nc |
NetCDF |
File Naming Convention
Files each contain the same data, and therefore have the same name. File extensions indicate the file type, as described above.
Example: Antarctica_ice_velocity.nc is a NetCDF file containing the data set.
File Size
Files range in size from 2769 KB to 348 MB.
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
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 map is provided at 900 m spacing with each data point containing information on the velocity in meters per year in x and y direction as defined by the polar stereographic grid (vx and vy respectively). An error estimate for the velocity magnitude is also provided. These estimates, however, should be used more as an indication of relative quality rather than absolute error. More information of the error estimates is provided the Quality Assessment section as well as in Rignot, et al. 2011.
Projection
The velocity map is provided in polar stereographic projection with true scale at 71° South.
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
This map provides velocity data for the Antarctic Ice Sheet, at 900 m spacing with each data point containing information on the velocity in meters per year in x and y direction as defined by the polar stereographic grid (vx and vy respectively). An error estimate for the velocity magnitude is also provided. These estimates, however, should be used more as an indication of relative quality rather than absolute error. More information of the error estimates is provided in the Quality Assessment section as well as in Rignot, et al. 2011.
Parameter 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 the product and its 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).
| 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 |
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
Total volume of the data set is 930 MB.
Software and Tools
Data are accessible using a variety of software.
Related Data Collections
- MEaSUREs Antarctic Grounding Line from Differential Satellite Radar Interferometry
- MEaSUREs InSAR-Based Ice Velocity Maps of Central Antarctica: 1997 and 2009
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 in the generation of the map:
- Speckle tracking in both along (azimuth) and across (range) track directions
Calculation of two dimensional offsets in amplitude imagery - 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 mosaic assembles 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.
Data Sources
Table 5 describes the data sources used in this data set.
| 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., J. Mouginot, and B. Scheuchl. 2011. Ice Flow of the Antarctic Ice Sheet. Science, Vol. 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 Glaciar 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
| 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.
| 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
5 October 2011
Document Revision Date
27 September 2012
Document URL
http://nsidc.org/data/docs/measures/nsidc0484_rignot/index.html
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