This data set is part of the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) program. This data set provides maps of glacier outlet areas, some of which have shown profound velocity changes over the MEaSUREs observation period from 2000 to 2011. The data are provided in addition to the ice-sheet-wide data from the related data set, MEaSUREs Greenland Ice Sheet Velocity Map from InSAR Data (NSIDC-0478). The InSAR Selected Glacier Site Velocity Maps are produced from TerraSAR-X (TSX) image pairs collected from January through November 2009, January through December 2010, and January through November 2011.
Data are available via FTP, in 4-byte Institute of Electrical and Electronics Engineers (IEEE) floating point format.
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.
The generation of this data set and its scientific interpretation are discussed in the following citation. Please acknowledge the use of this data set by referencing the following citation:
Joughin, I, B. E. Smith, I. M. Howat, T. Scambos, T. Moon. 2010. Greenland Flow Variability from Ice-Sheet-Wide Velocity Mapping. Journal of Glaciology, 56 (197), pp. 415-430. doi:10.3189/002214310792447734.
The following example shows how to cite the use of this data set in a publication. List the principal investigators, year of data set release, data set title, publisher: NSIDC, and digital media.
Joughin, I., I. Howat, B. Smith, T. Scambos. 2011. MEaSUREs Greenland Ice Velocity: Selected Glacier Site Velocity Maps from InSAR. Boulder, Colorado, USA: National Snow and Ice Data Center. Digital media.
| Category | Description |
|---|---|
| Data format | 4-byte big-endian Institute of Electrical and Electronics Engineers (IEEE) floating point format |
| Spatial coverage and resolution | The data set contains data for most of the outlet glaciers for the Greenland Ice Sheet. It is organized into 69 study sites. Southernmost Latitude: 60° N Northernmost Latitude: 82° N Westernmost Longitude: 20° W Easternmost Longitude: 70° W |
| Temporal coverage and resolution | January through November 2009, January through December 2010, and January through November 2011 |
| File naming convention | TSX_E68.80N_26Apr009_07May09.vx |
| File size | File size ranges from 178 bytes to 1.5 MB. |
| Parameters | Glacier surface velocity and measurement errors in meters per year |
| Procedures for obtaining data | Data are available via FTP. |
Dr. Ian Joughin
University of Washington
Applied Physics Laboratory
1013 NE 40th Street
Box 355640
Seattle, Washington 98105
USA
Dr. Ian Howat
Ohio State University
Byrd Polar Research Center
Scott Hall Room 108
1090 Carmack Road
Columbus, Ohio 43210
USA
Dr. Ben Smith
University of Washington
Polar Science Center Applied Physics Laboratory
University of Washington
Department of Earth and Space Sciences
Seattle, Washington 98195
USA
Dr. Ted Scambos
University of Colorado
Cooperative Institute for Research in Environmental Science
National Snow and Ice Data Center
CIRES, 449 UCB
Boulder, Colorado 80309
USA
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
These data were generated through a grant from the NASA MEaSUREs program.
Raw Data
Data files are in 4-byte big-endian IEEE floating point format with the same byte ordering used by non-Intel Macs and most workstations, not the standard PC byte order. No-data values are represented by -2.0e9. This may require that the user replace these values before applying analysis tools. There are separate files for velocity x (vx) and velocity y (vy) components. There are also accompanying pseudo-error estimates. Refer to the Error Estimates section, below. Accompanying geodat files provide grid descriptions corresponding to each velocity data file. Table 1 describes the file types.
| Filename | Description |
|---|---|
| TSX_E62.70N_23Apr09_04May09.vx TSX_E62.70N_23Apr09_04May09.vy |
Velocity products in 4-byte IEEE floating point format |
| TSX_E62.70N_23Apr09_04May09.vx.geodat TSX_E62.70N_23Apr09_04May09.vy.geodat |
Grid description files in .geodat format |
| TSX_E62.70N_23Apr09_04May09.ex TSX_E62.70N_23Apr09_04May09.ey |
Error values (1 sigma standard deviation) |
| TSX_E62.70N_23Apr09_04May09.meta | Metadata file in ASCII text format |
Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/DATASETS/nsidc0481_MEASURES_greenland_V01/ directory. This directory is divided into subdirectories based on the grid location, and then based on the type of data (TSX), and date of acquisition. Grid names and locations are provided under Spatial Coverage below.
Files are named according to the following convention and as described in Table 2:
Source_grid_startdate_enddate.xx
Where:
| Variable | Description |
|---|---|
| Source | Data Source
|
| grid | Grid is defined by the following:
|
| startdate | Beginning date of data collection (DDMMMYY) |
| enddate | End date of data collection (DDMMMYY) |
| xx | File extension
|
Example: TSX_E61.70N_23Apr09_04May09.vx is the displacement vector in X for the glacier on the East Coast of Greenland at 61.70°N, based on TerraSAR-X measurements from 23 April 2009 to 4 May 2009.
File size ranges from 178 bytes to 1.5 MB.
Table 3 details the grid name and locations, glaciers included in the grid, and dates for the available TSX data. The spatial coverage map below shows the locations of all the grids on a map of Greenland. Data are not available for all grids shown on the map.
Grid Name (Center Latitude) |
Lower Left Coordinate (Lat °N - Lon °W) |
Glaciers Included in Grid |
2009 TSX Data Available for Download |
2010 TSX Data Available for Download |
2011 TSX Data Available for Download |
|---|---|---|---|---|---|
| E61.70N | 61.3903 - 43.7671 |
|
February July September November |
April/May July August/September November |
Apr-30-2011 to May-11-2011 Aug-29-2011 to Sep-20-2011 Jul-05-2011 to Jul-27-2011 Nov-14-2011 to Nov-25-2011 |
| E62.10N | 61.801 - 43.2149 |
|
N/A | N/A | Mar-12-2011 to Mar-23-2011 |
| E62.55N | 62.2422 - 43.6371 |
|
February April/May July August September November |
February May July September November |
Apr-20-2011 to May-01-2011 Aug-30-2011 to Sep-21-2011 Feb-13-2011 to Feb-24-2011 Jul-06-2011 to Jul-17-2011 Nov-26-2011 to Dec-07-2011 |
| E63.00N | 62.7212 - 43.5332 |
|
February April/May July August September November |
February April/May July September November |
Apr-20-2011 to May-01-2011 Aug-30-2011 to Sep-21-2011 Feb-02-2011 to Feb-13-2011 Jul-06-2011 to Jul-17-2011 Nov-15-2011 to Nov-26-2011 |
| E63.35N | 63.0911 - 42.5656 |
|
February April/May July August September November |
January/February April/May July September November |
Apr-26-2011 to May-07-2011 Aug-03-2011 to Aug-25-2011 Feb-08-2011 to Feb-19-2011 Jul-12-2011 to Aug-03-2011 Nov-21-2011 to Dec-02-2011 |
| E63.85N | 63.5620 - 42.4419 |
|
February April/May July August September November |
February April/May July September November |
Apr-20-2011 to May-01-2011 Aug-30-2011 to Sep-21-2011 Feb-02-2011 to Feb-13-2011 Jul-06-2011 to Jul-17-2011 Nov-15-2011 to Nov-26-2011 |
| E64.35N | 64.0768 - 42.2688 |
|
January/February April/May July August September November |
January/February April/May July August/September November/December |
Apr-25-2011 to May-06-2011 Aug-24-2011 to Sep-15-2011 Jul-11-2011 to Jul-22-2011 Jul-22-2011 to Aug-24-2011 Nov-20-2011 to Dec-01-2011 |
| E64.65N | 64.3291 - 41.7539 |
|
N/A | N/A | Mar-08-2011 to Mar-19-2011 |
| E65.10N | 64.7987 - 41.8569 |
|
January/February April/May July August September November |
February April/May July September November |
Apr-20-2011 to May-01-2011 Aug-30-2011 to Sep-10-2011 Feb-13-2011 to Feb-24-2011 Jul-06-2011 to Jul-17-2011 Nov-15-2011 to Nov-26-2011 |
| E65.55N | 65.2242 - 40.5156 |
|
February April/May July August September November |
January/February April/May July August/September November |
Aug-03-2011 to Aug-25-2011 Aug-25-2011 to Sep-05-2011 Dec-02-2011 to Dec-24-2011 Feb-08-2011 to Feb-19-2011 Jul-12-2011 to Aug-03-2011 |
| E66.50N | 66.1973 - 39.1116 |
|
January/February April/May July August September November December |
April/May July September November |
Aug-09-2011 to Aug-20-2011 Jul-07-2011 to Jul-18-2011 Jun-04-2011 to Jun-15-2011 Mar-08-2011 to Mar-19-2011 Nov-16-2011 to Nov-27-2011 |
| E66.60N | 66.4197 - 37.4122 |
|
N/A | November November/December |
Aug-09-2011 to Aug-31-2011 Aug-31-2011 to Sep-11-2011 Jul-29-2011 to Aug-09-2011 May-02-2011 to May-13-2011 Nov-16-2011 to Nov-27-2011 |
| E67.55N | 67.2762 - 34.9643 |
|
January/February April/May July August September November |
February April/May July August/September November |
Apr-22-2011 to May-03-2011 Aug-21-2011 to Sep-12-2011 Feb-15-2011 to Mar-09-2011 Jul-08-2011 to Jul-19-2011 Nov-17-2011 to Nov-28-2011 |
| E68.80N | 68.4663 - 34.3672 |
|
January/February April/May June August September November Decemer |
April/May July/August September November |
Aug-21-2011 to Sep-01-2011 Jul-08-2011 to Jul-30-2011 Jun-05-2011 to Jun-16-2011 Mar-09-2011 to Mar-20-2011 Nov-17-2011 to Nov-28-2011 |
| E71.75N | 71.4887 - 30.9758 |
|
N/A | N/A | Mar-12-2011 to Mar-23-2011 Mar-27-2011 to Apr-07-2011 Mar-28-2011 to Apr-08-2011 |
| E78.90N | 78.7017 - 24.0968 |
|
N/A | N/A | Feb-25-2011 to Mar-08-2011 Mar-30-2011 to Apr-10-2011 |
| E79.40N | 79.190 - 24.0779 |
|
N/A | N/A | Mar-03-2011 to Mar-14-2011 |
| E81.35N | 81.1300 - 30.0074 |
|
N/A | N/A | Mar-27-2011 to Apr-07-2011 |
| E81.45N | 81.196 - 34.6273 |
|
N/A | N/A | Mar-08-2011 to Mar-19-2011 |
| W64.25N | 63.9263 - 49.8721 |
|
February April/May August September November |
February April/May August/September November |
Apr-29-2011 to May-10-2011 Aug-28-2011 to Sep-08-2011 Jul-15-2011 to Jul-26-2011 Jul-26-2011 to Aug-28-2011 Nov-13-2011 to Nov-24-2011 |
| W67.05N | 66.7183 - 50.3192 |
|
March July/August September November |
February April/May May June June/July July August August/September October/November November |
Aug-17-2011 to Aug-28-2011 Jul-15-2011 to Aug-06-2011 Jul-26-2011 to Aug-17-2011 Mar-16-2011 to May-10-2011 Nov-13-2011 to Nov-24-2011 |
| W69.10N | 68.7418 - 50.4126 |
|
January/February April/May July August September November |
February April/May July August/September September November/December |
Apr-12-2011 to Apr-23-2011 Apr-24-2011 to May-05-2011 Aug-02-2011 to Aug-13-2011 Aug-23-2011 to Sep-03-2011 Aug-23-2011 to Sep-14-2011 Feb-06-2011 to Feb-28-2011 Feb-16-2011 to Mar-10-2011 Jul-21-2011 to Aug-01-2011 Nov-18-2011 to Nov-29-2011 Nov-19-2011 to Nov-30-2011 |
| W69.95 | 69.6356 - 50.6122 |
|
N/A | N/A | Mar-27-2011 to Apr-07-2011 |
| W70.55N | 70.2285 - 50.9177 |
|
March June June/July August September November |
February May October/November November |
Apr-29-2011 to May-10-2011 Jul-15-2011 to Jul-26-2011 Nov-13-2011 to Nov-24-2011 |
| W71.65N | 71.3100 - 51.8327 |
|
January/February April/May July August September November |
April/May July August/September November/December |
Apr-24-2011 to May-05-2011 Aug-23-2011 to Sep-14-2011 Nov-19-2011 to Nov-30-2011 |
| W72.90N | 72.5829 - 54.8293 |
|
February April/May July September November |
April/May July August/September November |
Apr-30-2011 to May-11-2011 Aug-29-2011 to Sep-20-2011 Feb-01-2011 to Feb-12-2011 Jul-05-2011 to Jul-16-2011 Nov-14-2011 to Nov-25-2011 |
| W73.45N | 73.1520 - 55.6912 |
|
N/A | N/A | Mar-11-2011 to Mar-22-2011 |
| W73.75N | 73.1520 - 55.6912 |
|
N/A | N/A | Mar-05-2011 to Mar-16-2011 |
| W74.50N | 74.1506 - 56.4843 |
|
February April/May July September |
April/May July August/September November |
Apr-30-2011 to May-22-2011 Aug-29-2011 to Sep-20-2011 Feb-01-2011 to Feb-12-2011 Jul-05-2011 to Jul-16-2011 Nov-14-2011 to Nov-25-2011 |
| W74.95N | 74.5750 - 57.6463 |
|
January/February April/May July |
April/May July August/September November/December |
Apr-24-2011 to May-05-2011 Feb-17-2011 to Feb-28-2011 Jul-10-2011 to Aug-01-2011 Nov-19-2011 to Nov-30-2011 |
| W75.50N | 75.1264 - 58.5281 |
|
February April/May July September |
February April/May July September November |
Apr-20-2011 to May-01-2011 Feb-13-2011 to Feb-24-2011 Jul-06-2011 to Jul-17-2011 Nov-15-2011 to Nov-26-2011 |
| W75.85N | 75.4736 - 59.2722 |
|
N/A | N/A | Mar-01-2011 to Mar-23-2011 |
| W76.10N | 75.7205 - 60.0987 |
|
February April/May July September |
April/May July November |
Aug-29-2011 to Sep-09-2011 Feb-01-2011 to Feb-12-2011 Jul-05-2011 to Jul-16-2011 May-11-2011 to May-22-2011 Nov-14-2011 to Nov-25-2011 |
| W76.25N | 75.9067 - 61.2365 |
|
N/A | N/A | Feb-28-2011 to Mar-11-2011 |
| W76.35N | 75.7416 - 63.3988 |
|
N/A | N/A | Feb-27-2011 to Mar-10-2011 Mar-04-2011 to Mar-15-2011 |
| W76.40N | 76.0579 - 65.9643 |
|
N/A | N/A | Feb-26-2011 to Mar-09-2011 |
| W76.45N | 76.1084 - 67.6907 |
|
N/A | N/A | Feb-25-2011 to Mar-08-2011 |
| W77.55N | 77.0728 - 66.2296 |
|
N/A | N/A | Mar-05-2011 to Mar-27-2011 |
| W79.75N | 79.3702 - 65.1597 |
|
N/A | N/A | Mar-15-2011 to Mar-26-2011 |
| W80.75N | 79.9328 - 61.5545 |
|
N/A | N/A | Nov-09-2010 to Nov-20-2010 Nov-20-2010 to Dec-01-2010 |
| W81.25N | 80.9256 - 51.3505 |
|
N/A | N/A | Mar-14-2011 to Mar-25-2011 |
| S44.84W | 61.0923 - 45.3465 |
|
N/A | N/A | Mar-01-2011 to Mar-23-2011 |
| S45.43W | 61.2196 - 45.8994 |
|
N/A | N/A | Feb-24-2011 to Mar-29-2011 Mar-29-2011 to Apr-20-2011 |
| S46.31W | 60.9232 - 467807 |
|
N/A | N/A | Dec-14-2010 to Jan-05-2011 |
| S46.91W | 60.8876 - 47.3303 |
|
N/A | N/A | Dec-07-2010 to Dec-18-2010 |
100 meter

Figure 1. This map shows the locations of grids on a map of Greenland. Data
are not available for all grids shown on map.
Eventually data will be available for
more of the sites.
High Resolution Image.
Data are provided in subregions of a standard polar stereographic grid with a standard latitude of 70° N and rotation angle of -45° (sometimes specified as a longitude of 45° E). With this convention, the x-axis extends south from the North Pole along the 45° E meridian.
Location information is provided by the geodat files, in the following format:
Note. The origin specifies the polar stereographic coordinates for the center of the lower left pixel, the first sample in the file. This specification using the middle of the reference pixel is different than some GeoTIFF and other formats where the reference coordinates are specified for outer corner of the reference pixel.
# 2
;
;Image size (pixels) nx ny
;
600 720
;
;Pixel size (m) deltaX deltaY
;
100.000000 100.000000
;
;Origin, lower left corner (km)
Xo Yo
;
457.000000 -2319.000000
&
TSX data span January 2009 through November 2011.
The vx and vy files yield values of velocity in meters per year, in the x and y directions defined by the polar stereographic grid. The velocities are true values and not subject to the distance distortions present in a polar stereographic grid. In some areas small holes have been filled via interpolation. Interpolated values are identifiable as the locations where there is velocity data but no error estimate. Radar-derived velocities are determined using a combination of conventional InSAR and speckle tracking techniques (Joughin, 2002).
Error estimates are included for all non-interpolated radar-derived velocity vectors, in the files TSX_E62.70N_23Apr09_04May09.ex and TSX_E62.70N_23Apr09_04May09.ey. These estimates include the statistical uncertainty associated with the phase and speckle tracking error. Formal errors agree reasonably well with errors determined by comparison with GPS data (Joughin, 2002). These estimates, however, underestimate true uncertainty in several ways and as such should be used more as an indication of relative quality rather than absolute error.
See Joughin, 2002 for more detail on errors and how they are computed.
Data are available via FTP.
Total volume is 2.6 GB.
The data can be read using a variety of software. The following are sample codes for use in Matlab or IDL.
The following routines will read the data in Matlab.
% This function reads a standard mosaiced velocity data % |
The following code fragment can be used to write a complete program to read the data with IDL.
; |
The velocity maps in this data set were created using SAR data from the TerraSAR-X satellite. The methods included a combination of speckle tracking and conventional interferometry. For more detail, please see Joughin. 2002.
Synthetic Aperture Radar (SAR) data were obtained from the TerraSAR-X satellite.
Ahn, Y. and I. Howat. 2011. Efficient Automated Glacier Surface Velocity Measurement From Repeat Images Using Multi-Image/Multichip and Null Exclusion Feature Tracking. IEEE Transactions on Geoscience and Remote Sensing Vol. 49, No. 8. doi:10.1109/TGRS.2011.2114891.
Howat, I. M., J. E. Box, Y. Ahn, A. Herrington, E. M. McFadden. 2010. Seasonal Variability in the Dynamics of Marine-Terminating Outlet Glaciers in Greenland.Journal of Glaciology, 56(198), pp. 601-613. doi:10.3189/002214310793146232.
Joughin, I. 2002. Ice-Sheet Velocity Mapping: A Combined Interferometric and Speckle-Tracking Approach. Annals of Glaciology 34: 195-201. doi:10.3189/172756402781817978.
Joughin, I., W. Abdalati, and M. Fahnestock. 2004. Large fluctuations in speed on Greenland's Jakobshavn Isbræ glacier. Nature,Vol. 432: 608-610.
Joughin, I., B. Smith, I. M. Howat, T. Scambos, and T. Moon. 2010. Greenland Flow Variability from Ice-Sheet-Wide Velocity Mapping. Journal of Glaciology, 56 (197), pp. 415-430, doi: 10.3189/002214310792447734.
Joughin, I., R. Kwok, and M. Fahnestock, 1996. Estimation of Ice Sheet Motion Using Satellite Radar Interferometry: Method and Error Analysis with Application to Humboldt Glacier, Greenland. Journal of Glaciology 42(142) pp 564-575.
The following related Web sites provide additional information on MEaSUREs data and related data sets:
| Document | Description | URL |
|---|---|---|
| MEaSUREs Data Web site | NSIDC data Web site | http://nsidc.org/data/measures/ |
| NASA MEaSUREs Web site | NASA Measures Projects Web site | http://earthdata.nasa.gov/our-community/community-data-system-programs/measures-projects |
The following acronyms are used in this document.
| Acronym | Description |
|---|---|
| FTP | File Transfer Protocol |
| IDL | Interactive Data Language |
| MEaSUREs | Making Earth System Data Records for Use in Research Environments |
| NSIDC | National Snow and Ice Data Center |
| SAR | Synthetic Aperture Radar |
| TSX | TerraSAR-X |
| URL | Uniform Resource Locator |
19 May 2011
29 January 2013
http://nsidc.org/data/docs/measures/nsidc0481_joughin/index.html