MEaSUREs Greenland Ice Velocity: Selected Glacier Site Velocity Maps from InSAR

Summary

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 2012. 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. The InSAR Selected Glacier Site Velocity Maps are produced from TerraSAR-X (TSX) image pairs collected between January 2009 and December 2012.

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.

Citing These Data

Literature Citation

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

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.

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.

Joughin, I., I. Howat, B. Smith, T. Scambos. 2011. MEaSUREs Greenland Ice Velocity: Selected Glacier Site Velocity Maps from InSAR. Boulder, Colorado, USA: NASA DAAC at the National Snow and Ice Data Center. doi:10.5067/MEASURES/CRYOSPHERE/nsidc-0481.001.

Overview Table

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 51 study sites.

Southernmost Latitude: 60° N
Northernmost Latitude: 82° N
Easternmost Longitude: 20° W
Westernmost Longitude: 70° W
Temporal coverage and resolution January through November 2009
January through December 2010
January through November 2011
January through December 2012
File naming convention

TSX_E68.80N_26Apr09_07May09.vx
TSX_E68.80N_26Apr09_07May09.vx.geodat

File size File size ranges from 178 bytes to 4.6 MB.
Parameters Glacier surface velocity and measurement errors in meters per year
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. 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

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.

2. Detailed Data Description

Format

Raw Data

Data files are in 4-byte big-endian IEEE floating point format with the same byte ordering used by non-Intel Macs, 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.

Table 1. File Description
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

 

File and Directory Structure

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.

File Naming Convention

Files are named according to the following convention and as described in Table 2:

Source_grid_startdate_enddate.xx

Where:

Table 2. File Naming Convention
Variable Description
Source Data Source
  • TSX: TerraSAR-X
grid

Grid is defined by the following:

  • E, W, or S: East, West, or South Coast
  • Latitude in degrees, minutes
startdate Beginning date of data collection (DDMMMYY)
enddate End date of data collection (DDMMMYY)
xx File extension
  • vx: velocity x values
  • vy: velocity y values
  • ex: error x values
  • ey: error y values
  • geodat: location data files
  • meta: metadata file

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

File size ranges from 178 bytes to 4.6 MB.

Spatial Coverage

Table 3 details the grid names 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.

Table 3. Grid Details and Data Availability
Grid Name
(Center Lat)
Lower Left Coord
(Lat, Lon)
Glaciers Included
in Grid
TSX Data Available for Download
2009 2010 2011 2012
E61.10N¹ 60.8004, -43.9589 Unnamed near Danells
Danells
Kanderdluluk
Kap to Herlut to Trolle
Kap to Njordenskjold
N/A N/A N/A 02-28-12 to 03-10-12
E61.70N 61.3903, -43.7671 Anoritup Kangerdlua
Nappassorssuaq
Feb
Jul
Sep
Nov
Apr/May
Jul
Aug/Sep
Nov
04-30-11 to 05-11-11
07-05-11 to 07-27-11
08-29-11 to 09-20-11
11-14-11 to 11-25-11
07-24-12 to 08-15-12
08-15-12 to 08-26-12
11-11-12 to 11-22-12
E62.10N 61.801, -43.2149 Puisortuq North
Puisortuq South
N/A N/A 03-12-11 to 03-23-11 03-09-12 to 03-20-12
07-30-12 to 08-10-12
E62.55N 62.2422, -43.6371 Mogens
Tingmjarmiut
Feb
Apr/May
Jul
Aug
Sep
Nov
Feb
May
Jul
Sep
Nov
02-13-11 to 02-24-11
04-20-11 to 05-01-11
07-06-11 to 07-17-11
08-30-11 to 09-21-11
11-26-11 to 12-07-11
02-11-12 to 02-22-12
07-03-12 to 07-14-12
08-27-12 to 09-07-12
11-12-12 to 11-23-12
E63.00N 62.7212, -43.5332 Heimdal Feb
Apr/May
Jul
Aug
Sep
Nov
Feb
Apr/May
Jul
Sep
Nov
02-02-11 to 02-13-11
04-20-11 to 05-01-11
07-06-11 to 07-17-11
08-30-11 to 09-21-11
11-15-11 to 11-26-11
01-31-12 to 02-11-12
05-09-12 to 05-31-12
05-31-12 to 07-03-12
07-03-12 to 07-14-12
07-14-12 to 08-16-12
08-16-12 to 08-27-12
11-12-12 to 11-23-12
E63.35N 63.0911, -42.5656 Thrym
Sehested
Skinefaxe
Feb
Apr/May
Jul
Aug
Sep
Nov
Jan/Feb
Apr/May
Jul
Sep
Nov
02-08-11 to 02-19-11
04-26-11 to 05-07-11
07-12-11 to 08-03-11
08-03-11 to 08-25-11
11-21-11 to 12-02-11
02-17-12 to 02-28-12
06-06-12 to 06-17-12
06-17-12 to 07-09-12
07-09-12 to 07-20-12
08-22-12 to 09-13-12
11-18-12 to 11-29-12
E63.85N 63.5620, -42.4419 Bernstorf Feb
Apr/May
Jul
Aug
Sep
Nov
Feb
Apr/May
Jul
Sep
Nov
02-02-11 to 02-13-11
04-20-11 to 05-01-11
07-06-11 to 07-17-11
08-30-11 to 09-21-11
11-15-11 to 11-26-11
01-31-12 to 02-11-12
05-09-12 to 05-31-12
05-31-12 to 07-03-12
08-16-12 to 08-27-12
11-12-12 to 11-23-12
E64.35N 64.0768, -42.2688 Gyldenslove Jan/Feb
Apr/May
Jul
Aug
Sep
Nov
Jan/Feb
Apr/May
Jul
Aug/Sep
Nov/Dec
04-25-11 to 05-06-11
07-11-11 to 07-22-11
07-22-11 to 08-24-11
08-24-11 to 09-15-11
11-20-11 to 12-01-11
05-03-12 to 05-14-12
07-08-12 to 07-19-12
07-19-12 to 08-21-12
08-21-12 to 09-01-12
11-17-12 to 11-28-12
E64.65N 64.3291, -41.7539 Fridtjof N/A N/A 03-08-11 to 03-19-11 03-05-12 to 03-16-12
07-26-12 to 08-06-12
E65.10N 64.7987, -41.8569 Koge Bugt Jan/Feb
Apr/May
Jul
Aug
Sep
Nov
Feb
Apr/May
Jul
Sep
Nov
02-13-11 to 02-24-11
04-20-11 to 05-01-11
07-06-11 to 07-17-11
08-30-11 to 09-10-11
11-15-11 to 11-26-11
01-31-12 to 02-11-12
05-31-12 to 06-22-12
06-22-12 to 07-25-12
07-25-12 to 08-16-12
11-12-12 to 12-04-12
E65.55N 65.2242, -40.5156 Ikertivaq
Pamiatig
Feb
Apr/May
Jul
Aug
Sep
Nov
Jan/Feb
Apr/May
Jul
Aug/Sep
Nov
02-08-11 to 02-19-11
07-12-11 to 08-03-11
08-03-11 to 08-25-11
08-25-11 to 09-05-11
12-02-11 to 12-24-11
02-06-12 to 02-17-12
04-23-12 to 05-15-12
07-09-12 to 07-20-12
07-20-12 to 08-22-12
08-22-12 to 09-13-12
11-18-12 to 11-29-12
E66.50N 66.1973, -39.1116 Fenris
Helheim
Jan/Feb
Apr/May
Jul
Aug
Sep
Nov
Dec
Apr/May
Jul
Sep
Nov
03-08-11 to 03-19-11
06-04-11 to 06-15-11
07-07-11 to 07-18-11
08-09-11 to 08-20-11
11-16-11 to 11-27-11
01-10-12 to 01-21-12
01-21-12 to 02-01-12
02-01-12 to 02-12-12
02-12-12 to 02-23-12
02-23-12 to 03-05-12
03-05-12 to 03-16-12
03-16-12 to 04-07-12
04-02-12 to 04-13-12
04-07-12 to 04-29-12
04-28-12 to 05-09-12
04-29-12 to 06-01-12
05-09-12 to 05-20-12
05-20-12 to 05-31-12
06-18-12 to 06-29-12
06-22-12 to 07-03-12
07-03-12 to 07-14-12
07-15-12 to 07-26-12
07-21-12 to 08-01-12
07-26-12 to 08-06-12
08-01-12 to 08-12-12
08-06-12 to 08-17-12
08-17-12 to 08-28-12
08-28-12 to 09-08-12
09-08-12 to 10-11-12
10-11-12 to 10-22-12
10-22-12 to 11-02-12
11-02-12 to 11-24-12
11-24-12 to 12-05-12
12-05-12 to 12-16-12
12-16-12 to 12-27-12
12-27-12 to 01-07-13
E66.60N¹ Pre 01/01/2012:
66.4197, -37.4122
Post 01/01/2012:
66.3305, -37.4428
Midgard
Midgard Nord
N/A Nov
Nov/Dec
05-02-11 to 05-13-11
07-29-11 to 08-09-11
08-09-11 to 08-31-11
08-31-11 to 09-11-11
11-16-11 to 11-27-11
02-01-12 to 02-12-12
07-04-12 to 07-15-12
09-08-12 to 09-30-12
11-13-12 to 11-24-12
E66.90 N¹ 66.5045, -36.2923 kruuse
steenstrup to east
tasiliaq
N/A N/A N/A 03-06-12 to 03-17-12
E67.55N 67.2762, -34.9643 Nordre Parallel Gletscher
Nordre
Jan/Feb
Apr/May
Jul
Aug
Sep
Nov
Feb
Apr/May
Jul
Aug/Sep
Nov
02-15-11 to 03-09-11
04-22-11 to 05-03-11
07-08-11 to 07-19-11
08-21-11 to 09-12-11
11-17-11 to 11-28-11
02-02-12 to 02-13-12
04-30-12 to 05-11-12
07-05-12 to 07-27-12
07-27-12 to 08-29-12
08-29-12 to 09-09-12
11-14-12 to 11-25-12
E68.80N 68.4663, -34.3672 Kangerdlugssuaq
Nordfjord
Jan/Feb
Apr/May
Jun
Aug
Sep
Nov
Dec
Apr/May
Jul/Aug
Sep
Nov
03-09-11 to 03-20-11
06-05-11 to 06-16-11
07-08-11 to 07-30-11
08-21-11 to 09-01-11
11-17-11 to 11-28-11
02-02-12 to 02-13-12
02-13-12 to 02-24-12
02-24-12 to 03-06-12
03-06-12 to 03-28-12
03-17-12 to 03-28-12
03-28-12 to 04-08-12
05-05-12 to 05-16-12
06-24-12 to 07-05-12
07-05-12 to 07-16-12
07-10-12 to 07-21-12
07-16-12 to 07-27-12
07-27-12 to 08-18-12
08-18-12 to 08-29-12
08-29-12 to 09-09-12
09-09-12 to 10-12-12
10-12-12 to 10-23-12
10-23-12 to 11-03-12
11-03-12 to 11-14-12
11-14-12 to 11-25-12
11-25-12 to 12-06-12
12-06-12 to 12-17-12
12-17-12 to 12-28-12
12-28-12 to 01-08-13
E71.75N 71.4887, -30.9758 Daugaard-Jensen N/A N/A 03-12-11 to 03-23-11
03-27-11 to 04-07-11
03-28-11 to 04-08-11
02-27-12 to 03-09-12
03-02-12 to 03-13-12
03-03-12 to 03-14-12
E78.90N 78.7017, -24.0968 Zach N/A N/A 02-25-11 to 03-08-11
03-30-11 to 04-10-11
03-05-12 to 03-16-12
03-27-12 to 04-07-12
E79.40N 79.190, -24.0779 Fjorden N/A N/A 03-03-11 to 03-14-11 02-29-12 to 03-11-12
E81.35N 81.1300, -30.0074 Hagan N/A N/A 03-27-11 to 04-07-11 03-02-12 to 03-13-12
E81.45N 81.196, -34.6273 Acad N/A N/A 03-08-11 to 03-19-11 03-05-12 to 03-16-12
W61.70N¹ 61.4746, -48.4912 Sermiligarssuk N/A N/A N/A 03-08-12 to 03-19-12
W62.10N¹ 61.8077, -49.0172 Nigerdlikasik
Avangnardleq
Ukassorssuaq
N/A N/A N/A 03-02-12 to 03-13-12
W64.25N 63.9263, -49.8721 Kangia
Qamanarssup
Feb
Apr/May
Aug
Sep
Nov
Feb
Apr/May
Aug/Sep
Nov
04-29-11 to 05-10-11
07-15-11 to 07-26-11
07-26-11 to 08-28-11
08-28-11 to 09-08-11
11-13-11 to 11-24-11
02-09-12 to 02-20-12
05-07-12 to 05-18-12
07-01-12 to 07-23-12
09-05-12 to 09-16-12
11-10-12 to 11-21-12
W67.05N 66.7183, -50.3192 Russell Mar
Jul/Aug
Sep
Nov
Feb
Apr/May
May
Jun
Jun/Jul
Jul
Aug
Aug/Sep
Oct/Nov
Nov
03-16-11 to 05-10-11
07-15-11 to 08-06-11
07-26-11 to 08-17-11
08-17-11 to 08-28-11
11-13-11 to 11-24-11
N/A
W69.10N 68.7418, -50.4126 Alangordliup
Jakobshavn
Torssukatak
Jan/Feb
Apr/May
Jul
Aug
Sep
Nov
Feb
Apr/May
Jul
Aug/Sep
Sep
Nov/Dec
02-06-11 to 02-28-11
02-16-11 to 03-10-11
04-12-11 to 04-23-11
04-24-11 to 05-05-11
07-21-11 to 08-01-11
08-02-11 to 08-13-11
08-23-11 to 09-03-11
08-23-11 to 09-14-11
11-18-11 to 11-29-11
11-19-11 to 11-30-11
01-03-12 to 01-25-12
01-08-12 to 01-19-12
01-13-12 to 01-24-12
01-19-12 to 01-30-12
01-23-12 to 02-03-12
01-30-12 to 02-10-12
02-03-12 to 02-14-12
02-04-12 to 02-15-12
02-10-12 to 02-21-12
02-14-12 to 02-25-12
02-15-12 to 02-26-12
02-21-12 to 03-14-12
02-25-12 to 03-07-12
02-27-12 to 03-09-12
03-07-12 to 03-18-12
03-09-12 to 03-20-12
03-14-12 to 03-25-12
03-25-12 to 04-05-12
04-21-12 to 05-02-12
05-12-12 to 05-23-12
05-24-12 to 06-04-12
06-03-12 to 06-14-12
06-04-12 to 06-15-12
06-05-12 to 06-16-12
06-10-12 to 06-21-12
06-14-12 to 06-25-12
06-21-12 to 07-02-12
07-02-12 to 07-13-12
07-06-12 to 07-17-12
07-07-12 to 07-18-12
07-08-12 to 07-19-12
07-19-12 to 07-30-12
07-30-12 to 08-10-12
08-09-12 to 08-20-12
08-10-12 to 08-21-12
08-20-12 to 08-31-12
08-20-12 to 08-31-12
08-21-12 to 09-01-12
08-31-12 to 09-11-12
09-11-12 to 09-22-12
09-22-12 to 10-03-12
10-03-12 to 10-14-12
10-04-12 to 10-15-12
10-14-12 to 10-25-12
10-15-12 to 10-26-12
11-04-12 to 11-15-12
11-15-12 to 11-26-12
11-16-12 to 11-27-12
11-16-12 to 11-27-12
11-17-12 to 11-28-12
11-26-12 to 12-07-12
11-27-12 to 12-08-12
11-28-12 to 12-09-12
12-08-12 to 12-19-12
12-09-12 to 12-20-12
12-20-12 to 12-31-12
12-29-12 to 01-09-13
12-31-12 to 01-11-13
W69.95 69.6356, -50.6122 Kangilerngata
Kujatdleq
Torsukatat
N/A N/A 03-27-11 to 04-07-11 03-02-12 to 03-13-12
W70.55N 70.2285, -50.9177 Lille
Sermilik
Kangigdleq
Store
Mar
Jun
Jun/Jul
Aug
Sep
Nov
Feb
May
Oct/Nov
Nov
04-29-11 to 05-10-11
07-15-11 to 07-26-11
11-13-11 to 11-24-11
02-09-12 to 02-20-12
05-07-12 to 05-18-12
09-05-12 to 09-16-12
11-10-12 to 11-21-12
W71.65N 71.3100, -51.8327 Kangerdlugssup
Rink
Jan/Feb
Apr/May
Jul
Aug
Sep
Nov
Apr/May
Jul
Aug/Sep
Nov/Dec
04-24-11 to 05-05-11
08-23-11 to 09-14-11
11-19-11 to 11-30-11
02-15-12 to 02-26-12
04-21-12 to 05-02-12
07-07-12 to 07-18-12
08-31-12 to 09-11-12
11-16-12 to 11-27-12
W72.00N¹ 71.6540, -52.8014 Ingia
Umiamako
N/A N/A N/A 03-03-12 to 03-14-12
W72.90N 72.5829, -54.8293 Alangorssup Sermia
Upernavik
Feb
Apr/May
Jul
Sep
Nov
Apr/May
Jul
Aug/Sep
Nov
02-01-11 to 02-12-11
04-30-11 to 05-11-11
07-05-11 to 07-16-11
08-29-11 to 09-20-11
11-14-11 to 11-25-11
01-30-12 to 02-10-12
04-27-12 to 05-08-12
07-02-12 to 07-24-12
07-24-12 to 08-26-12
08-26-12 to 09-06-12
11-22-12 to 12-03-12
W73.45N 73.1520, -55.6912 Kakivfat
Giesecke
Nutarmiut
Tuvssaq
N/A N/A 03-11-11 to 03-22-11 02-26-12 to 03-08-12
07-07-12 to 07-18-12
08-31-12 to 09-11-12
11-16-12 to 11-27-12
W73.75N 73.1520, -55.6912 Comell
Sugarloaf
Ussing
N/A N/A 03-05-11 to 03-16-11 03-02-12 to 03-13-12
07-01-12 to 07-23-12
09-16-12 to 09-27-12
12-13-12 to 12-24-12
W74.50N 74.1506, -56.4843 Cornel
Alison
Igdlulik
Feb
Apr/May
Jul
Sep
Apr/May
Jul
Aug/Sep
Nov
02-01-11 to 02-12-11
04-30-11 to 05-22-11
07-05-11 to 07-16-11
08-29-11 to 09-20-11
11-14-11 to 11-25-11
01-30-12 to 02-10-12
04-27-12 to 05-08-12
07-02-12 to 07-24-12
07-24-12 to 08-26-12
08-26-12 to 09-06-12
11-22-12 to 12-03-12
W74.95N 74.5750, -57.6463 Hays
Kjers
Jensen
Jan/Feb
Apr/May
Jul
Apr/May
Jul
Aug/Sep
Nov/Dec
02-17-11 to 02-28-11
04-24-11 to 05-05-11
07-10-11 to 08-01-11
11-19-11 to 11-30-11
02-04-12 to 02-15-12
04-21-12 to 05-02-12
07-07-12 to 07-18-12
07-18-12 to 08-20-12
08-20-12 to 08-31-12
11-16-12 to 11-27-12
W75.50N 75.1264, -58.5281 Dietrichsons
Steenstrup
Sverdrups
Feb
Apr/May
Jul
Sep
Feb
Apr/May
Jul
Sep
Nov
02-13-11 to 02-24-11
04-20-11 to 05-01-11
07-06-11 to 07-17-11
11-15-11 to 11-26-11
01-31-12 to 02-11-12
07-03-12 to 07-14-12
08-27-12 to 09-07-12
11-12-12 to 11-23-12
W75.85N 75.4736, -59.2722 South of Nansen
Nansen
Nordenskiold
N/A N/A 03-01-11 to 03-23-11 02-27-12 to 03-09-12
07-08-12 to 07-19-12
09-01-12 to 09-12-12
11-17-12 to 11-28-12
W76.10N 75.7205, -60.0987 Kong Oscar
Nordenskiold
Nutarmiut
Feb
Apr/May
Jul
Sep
Apr/May
Jul
Nov
02-01-11 to 02-12-11
05-11-11 to 05-22-11
07-05-11 to 07-16-11
08-29-11 to 09-09-11
11-14-11 to 11-25-11
01-30-12 to 02-10-12
04-27-12 to 05-08-12
07-02-12 to 07-13-12
08-26-12 to 09-06-12
11-11-12 to 11-22-12
W76.25N 75.9067, -61.2365 Balgoni
Docker
Fisher
Igssuarssuit
Leven
N/A N/A 02-28-11 to 03-11-11 N/A
W76.35N 75.7416, -63.3988 Mohn
Gade
Meteor
Yngvar Nielson
N/A N/A 02-27-11 to 03-10-11
03-04-11 to 03-15-11
03-01-12 to 03-12-12
03-07-12 to 03-18-12
W76.40N 76.0579, -65.9643 Savigssuaq Helland
Sidebriks
N/A N/A 02-26-11 to 03-09-11 03-06-12 to 03-17-12
W76.45N 76.1084, -67.6907 Dedodes
Harald Moltke
N/A N/A 02-25-11 to 03-08-11 03-05-12 to 03-16-12
W77.55N 77.0728, -66.2296 Leidy
Mane
Heilprin
Mellville
Tracy
N/A N/A 03-05-11 to 03-27-11 03-02-12 to 03-13-12
W79.75N 79.3702, -65.1597 Humboldt N/A N/A 03-15-11 to 03-26-11 03-01-12 to 03-12-12
W80.75N 79.9328, -61.5545 Petermann N/A N/A 11-09-10 to 11-20-10
11-20-10 to 12-01-10
03-07-12 to 03-18-12
07-28-12 to 08-08-12
W81.25N 80.9256, -51.3505 Ryder N/A N/A 03-14-11 to 03-25-11 N/A
W81.5N² 81.1505, -46.6109 Chow N/A N/A N/A 03-08-12 to 03-19-12
S44.84W 61.0923, -45.3465 Kiagtut
Qorqup
N/A N/A 03-01-11 to 03-23-11 02-27-12 to 03-09-12
S45.43W 61.2196, -45.8994 Eqalorutsit Kangigdlit
Sermia
N/A N/A 02-24-11 to 03-29-11
03-29-11 to 04-20-11
03-04-12 to 03-15-12
07-25-12 to 08-16-12
S46.31W¹ Pre 01/01/2012:
60.9232, -46.7807
Post 01/01/2012:
60.9216, -46.7833
Eqalorutsit Kangigdlit
Sermia West
N/A N/A 12-14-10 to 01-05-11 03-31-12 to 04-11-12
S46.91W 60.8876, -47.3303 Qaleragdlit
Naujat
Sermilik
N/A N/A 12-07-10 to 12-18-10 03-24-12 to 04-04-12
¹Grid expanded in 2012. Refer to Figure 1 below. New perimeter indicated in blue.
²Grid added in 2012. Perimeter indicated in blue.


Spatial Resolution

100 meter

Spatial Coverage Map

locator map
Figure 1. This map shows the locations of grids on a map of Greenland. New grids for 2012 are shown in blue. Data are not available for all grids shown on map. Eventually data will be available for more of the sites.
High Resolution Image.

Projection

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° W). With this convention, the y-axis extends south from the North Pole along the 45° W 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 differs from that used in some GeoTIFF and other formats where the reference coordinates are specified for outer corner of the reference pixel.

Sample .geodat file

TSX_E61.70N_21Apr10_02May10.ex.geodat:

# 2
;
; Image size (pixels) nx ny
;
566 692
;
; Pixel size (m) deltaX deltaY
;
100.000000 100.000000
;
; Origin, lower left corner (km) Xo Yo
;
68.000000 -3162.100000
&

Sample .meta file

TSX_E61.70N_21Apr10_02May10.meta:

Central Julian Date (CE) for Pair = 2455314.355
First Image Date (MM:DD:YYYY) = Apr:21:2010
Second Image Date (MM:DD:YYYY) = May:02:2010
Nominal Time for Pair (HH:MM:SS) = 20:30:31
Sensor = TSX/TDX
Product Center Latitude = 61.68260
Product Center Longitude = -43.23729
Production Date/Time = Sep-26-2012-11:48:36

Temporal Coverage

TSX data span January 2009 through December 2012.

Parameter or Variable

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

Error estimates are included for all non-interpolated radar-derived velocity vectors as in, for example, the files TSX_E61.70N_23Apr09_04May09.ex and TSX_E61.70N_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.

3. Data Access and Tools

Data Access

Data are available via FTP.

Volume

Total volume is approximately 3.2 GB.

Software and Tools

The data can be read using a variety of software. The following are sample codes for use in Matlab or IDL.

Reading data with Matlab

The following routines will read the data in Matlab.

% This function reads a standard mosaiced velocity data
% set and returns arrays with the data and the geodat info.
%
function [vx,vy,xd]= readvelocity(rootname)
%
% Get geodat info
%
xd=readgeodat(strcat(rootname,'.vx.geodat'));
%
% Vx component
%
fid = fopen(strcat(rootname,'.vx'),'r','ieee-be');
[vx,count]=fread(fid,[xd(1,1) xd(1,2)],'float32');
fclose(fid);
%
% Vy component
%
fid = fopen(strcat(rootname,'.vy'),'r','ieee-be');
[vy,count]=fread(fid,[xd(1,1) xd(1,2)],'float32');
fclose(fid);

%
% Read a geodat file
%
function xgeo=readgeodat(filein)
fid = fopen(filein,'r');
xgeo=zeros(3,2);
i=1;
while ~feof(fid),
  line=fgets(fid);
  [A,count]=sscanf(line,'%f %f',[1 2]);
  if(count == 2)
     xgeo(i,:)=A;
     i=i+1;
  end
end
fclose(fid);=

Reading data with IDL

The following code fragment can be used to write a complete program to read vx or vy velocity data with IDL.

;
; Similar to matlab program
;
get_lun,lun
openr,lun,filename
buffer=fltarr(xs)
image=fltarr(xs,ys)
for i=0,ys-1 do begin
   readu,lun,buffer
   buffer=swap_endian(buffer,/swap_if_little_endian)  ; This is needed on a PC
   image(*,i) = buffer
endfor

Related Data Collections

4. Data Acquisition and Processing

Theory of Measurements

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.

Sensor or Instrument Description

Synthetic Aperture Radar (SAR) data were obtained from the TerraSAR-X satellite.

5. References and Related Publications

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:

Table 4. Related Documents
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

6. Document Information

Acronyms

The following acronyms are used in this document.

Table 5. Acronyms and Abbreviations
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

Document Creation Date

May 2011

Document Revision Date

July 2014

Document URL

http://nsidc.org/data/docs/measures/nsidc0481_joughin/index.html