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Data Set ID:
NSIDC-0646

MEaSUREs Greenland Ice Velocity: Selected Glacier Site Velocity Maps from Optical Images, Version 2

This data set, part of the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) program, consists of mean monthly velocity maps for selected glacier outlet areas. The maps are generated by tracking visible features between optical image pairs acquired by the Landsat 4 and 5 Thematic Mapper (TM), the Landsat 7 Enhanced Thematic Mapper Plus (ETM+), the Landsat 8 Operational Land Imager (OLI), and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER).

See Greenland Ice Mapping Project (GIMP) for related data.

Version Summary:

Changes for Version 2 include:

  • A correction was applied in the processing, which caused error values to appear as NaNs in some of the data
  • A more aggressive filtering method was applied to remove small, isolated clusters of data
  • Cross-path Landsat pairs were used to fill in temporal gaps in the 2016 data, using the MEaSUREs Greenland Ice Mapping Project (GIMP) Digital Elevation Model from GeoEye and WorldView Imagery and the orthorectifcation algorithm of Rosenau 2012
  • Spatial coverage was expanded to include more outlet glaciers in Greenland
  • Temporal coverage was expanded
  • To reduce overall size of the data set, GeoTIFFs are produced using Lempel–Ziv–Welch LZW lossless compression

Geographic Coverage

Parameter(s):
  • Snow/Ice > Ice Velocity
Spatial Coverage:
  • N: 82, S: 60, E: -20, W: -70

Spatial Resolution:
  • 100 m x 100 m
Temporal Coverage:
  • 1 March 1985 to 30 October 2016
Temporal Resolution: 1 month
Data Format(s):
  • GeoTIFF
  • PNG
Platform(s) LANDSAT-4, LANDSAT-5, LANDSAT-7, LANDSAT-8, TERRA
Sensor(s): ASTER, ETM+, OLI, TM
Version: V2
Data Contributor(s): Ian Howat
Data Citation

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Howat, I. 2017. MEaSUREs Greenland Ice Velocity: Selected Glacier Site Velocity Maps from Optical Images, Version 2. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: http://dx.doi.org/10.5067/VM5DZ20MYF5C. [Date Accessed].

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Detailed Data Description

Format

This data set is organized into 74 study sites. Study sites in this data set correspond to geographical sub-regions of Greenland. The name of each sub-region reflects its center latitude. Table 2 under the Spatial Coverage section of this document lists the name (center latitude) of each sub-region, the latitude and longitude of its lower left corner, and the geographical features it contains.

The following files are provided for each site:

  • velocity browse image (PNG)
  • component velocity in the x-direction (GeoTIFF)
  • component velocity in the y-direction (GeoTIFF)
  • error estimates in the x-direction (GeoTIFF)
  • error estimates in the y-direction (GeoTIFF)
  • metadata file (ASCII text)
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File and Directory Structure

Data are available via HTTPS: https://daacdata.apps.nsidc.org/pub/DATASETS/nsidc0646_MEASURES_greenland_vel_optical_v2.

In this directory, there are 74 folders, 1 for each study site, and within each of these folders are subfolders for each date of acquisition.  Each subfolder contains six data files.

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File Naming Convention

This section describes the naming convention for this product with an example. Refer to Table 1 for descriptions of the values in the file naming convention.

File Naming Convention:
OPT_[sub-region]_[date]_[datum]_[v2].[ext]

Example File Names:

  • OPT_E61.10N_1999-09_v2.png
  • OPT_E61.10N_1999-09_vx_v2.tif
  • OPT_E61.10N_1999-09_vy_v2.tif
  • OPT_E61.10N_1999-09_ex_v2.tif
  • OPT_E61.10N_1999-09_ey_v2.tif
  • OPT_E61.10N_1999-09_v2.meta
Table 1. File Name Variables and Descriptions
Variable Description
OPT Velocities derived from optical image pairs acquired by Landsat 8 OLI, Landsat 7 ETM+, Landsat 4 TM, Landsat 5 TM, ASTER or a combination.
sub-region  Sub-region names are defined as follows:
  • E, W, or S: East, West, or South Coast
  • Center latitude in degrees, minutes
date Date of acquisition (YYYY-MM)
datum Component velocity or component error estimate:
  • vx: x component of velocity
  • vy: y component of velocity
  • ex: x component of error
  • ey: y component of error
v2 version number
ext File extension:
  • png: Portable Network Graphic file
  • tif: GeoTIFF-formatted file
  • meta: ASCII text file. Contains image dates, production date, sensor combinations, and geographical information.
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File Size

Each data file ranges in size from 0.3 MB to 5.1 MB.

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Volume

The total data volume is approximately 23 GB.

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Spatial Coverage

This data set contains velocity maps for most of the outlet glaciers on the Greenland Ice Sheet. The study area lies within the following bounding box:

  •  Southernmost Latitude: 60° N
  •  Northernmost Latitude: 82° N
  •  Easternmost Longitude: 20° W
  •  Westernmost Longitude: 70° W

Spatial Resolution

100 m

Projection and Grid Description

GeoTIFFs are provided in a WGS 84 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 (EPSG:3413).

Table 2. Sub-Region Names, Locations, and Geographical Features

Sub-Region Name

  • Latitude, Longitude (lower left corner)
Geographical Features in Grid
E61.10N
  • 60.8004, -43.9589
  • Unnamed glacier near Danell Fjord
  • Danells
  • Kanderdluluk Fjord
  • Cape Herluf Trolle
  • Cape Tordenskjold
E61.70N
  • 61.3903, -43.7671
  • Anorituup Kangerlua Fjord
  • Napasorsuaq Fjord
E62.10N
  • 61.801, -43.2149
  • Puisortoq Glacier (north)
  • Puisortoq Fjord (south)
E62.55N
  • 62.2422, -43.6371
  • Mogens Heinesen Fjord
  • Timmiarmiut Fjord
E63.00N
  • 62.7212, -43.5332
  • Heimdal Glacier
E63.35N
  • 63.0911, -42.5656
  • Thrym Glacier
  • Sehested Fjord
  • Skinfaxe Glacier
E63.85N
  • 63.5620, -42.4419
  • Bernstorffs Fjord
E64.35N
  • 64.0768, -42.2688
  • Gyldenlove Fjord
E64.65N
  • 64.3291, -41.7539
  • Fridtjof Nansens Peninsula
E65.10N
  • 64.7987, -41.8569
  • Koge Bay
E65.55N
  • 65.2242, -40.5156
  • Ikertivaq Sound
  • Pamiatig
E66.00N
  • 65.9492, -38.6334
  • Bruckner
  • Heim
E66.50N
  • 66.1973, -39.1116
  • Fenris Glacier
  • Helheim Glacier
E66.60N
  • 66.3305, -37.4428
  • Midgard Glacier
  • Midgard North
E66.90N
  • 66.5045, -36.2923
  • Kruuse Fjord
  • Steenstrup Glacier
  • Tasiilaq Fjord
E67.55N
  • 67.2762, -34.9643
  • Norde Parallel Glacier
  • Nordre
E68.05N
  • 67.9148, -33.9170
  • Hutchinson Glacier
E68.50N
  • 68.3044, -31.1040
  • Courtauld Glacier
  • Frederiksborg Glacier
  • Christian IV Glacier
  • Sorgenfri Glacier
E68.52N
  • 68.3044, -31.1040
  • Schjelderup Glacier
  • Sorgenfri Glacier
E68.75N
  • 68.5151, -30.1133
  • Rosenborg
  • Kronborg
  • Borggraven
E68.80N
  • 68.4663, -34.3672
  • Kangerdlussuaq Glacier
  • Nordfjord Glacier
E68.95N
  • 68.7516, -27.7071
  • Sortebrae
E69.30N
  • 69.1760, -26.1549
  • Barclay Bay
  • unnamed glacier
E69.80N
  • 69.6752, -25.0537
  • Steno
  • Bartholin
E69.90N
  • 69.8224, -29.5537
  • unnamed glaciers
E70.10N
  • 70.0023, -26.7390
  • Syd Glacier
E70.40N
  • 70.0488, -30.6613
  • Rolige Glacier
E71.05N
  • 70.9090, -30.0003
  • Harefjord
  • Rypefjord
  • unnamed glacier
E71.75N
  • 71.4887, -30.9758
  • Daugaard-Jensen Glacier
E71.95N
  • 71.7410, -29.9742  
  • Daugard-Jensen Glacier
E74.05N
  • 73.9482, -26.4408
  • Waltershausen
E75.15N
  • 75.1665, -23.2614
  • Heinkel
E75.70N
  • 75.6225, -23.3212
  • Ejnar Mikkelsen
  • Storm Stejl
E76.55N
  • 76.2080, -24.5210
  • Bistrup
  • Brede
  • Storstrommen
E77.55N
  • 77.51625, -22.7208
  • Kofoed-Hansen
E78.95N
  • 78.7851, -22.2120
  • Gammel Hellerup Glacier
E79.40N
  • 79.190, -24.0779
  • Fjorden
W61.30N
  • 61.2671-47.8697
  • unnamed
W61.70N
  • 61.4746, -48.4912
  • Sermiligarssuk Fjord
W62.10N
  • 61.8077, -49.0172
  • Nigerdlikasik Glacier
  • Avangnardleq Glacier
  • Ukassorssuaq
W63.05N
  • 62.9804, -49.7627
  • Nakaissorssuaq
W64.25N
  • 63.9263, -49.8721
  • Kangiata Nunata Sermia Glacier
  • Quamanarssup Glacier
W64.75N
  • 64.4610, -50.1732
  • Ujarassuit Paauat Fjord
  • Narsap Sermia Glacier
W67.95N
  • 67.9133, -50.3921
  • Usulluup
W69.10N
  • 68.7418, -50.4126
  • Alangordliup Sermia Glacier
  • Jakobshavn Isbræ Glacier
  • Torsukattak Glacier
W69.95N
  • 69.6356, -50.6122
  • Kangilerngata Sermia Glacier
  • Kujatdleq Glacier
  • Torsukattak Fjord
W70.55N
  • 70.2285, -50.9177
  • Lille Glacier
  • Sermilik Glacier
  • Kangilleq Glacier
  • Store Glacier
W70.90N
  • 70.7542, -50.9613
  • Perdlerfiup Sermis Glacier
  • Silardleq
W71.25N
  •  71.1917, -51.5587
  • Kangerdluarssup
W71.65N
  • 71.3100, -51.8327
  • Kangerluarsuk Glacier
  • Rink Glacier
W72.00N
  • 71.6540, -52.8014
  • Inngia Fjord
  • Umiammakku Glacier
W72.90N
  • 72.5829, -54.8293
  • Alangorssup Sermia Glacier
  • Upernavik Isstorm Glacier
W73.45N
  • 73.1520, -55.6912
  • Kakivfait Sermiat Glacier
  • Giesecke Glacier
  • Nutarmiut Glacier
  • Tuvssaq (populated area)
W73.75N
  • 73.1520, -55.6912
  • Cornell Glacier
  • Sugarloaf Bugt (sound)
  • Ussing Glacier
W74.50N
  • 74.1506, -56.4843
  • Cornel Glacier
  • Alison Bugy (bay)
  • Illulik (populated area)
W74.95N
  • 74.5750, -57.6463
  • Hays Glacier
  • Kjer Glacier
  • Jensen Glacier
W75.50N
  • 75.1264, -58.5281
  • Dietrichson Glacier
  • Steenstrup Glacier
  • Sverdrup Glacier
W75.85N
  • 75.4736, -59.2722
  • Nansen Glacier
  • Nordenskiold Glacier
W76.10N
  • 75.7205, -60.0987
  • Kong Oscar Glacier
  • Nordenskiold Glacier
  • Nutarmiut
W76.25N
  • 75.9067, -61.2365
  • Balgoni
  • Docker Smith Glacier
  • Fisher
  • Igssuarssuit Sermia Glacier
  • Leven
W76.30N
  • 76.1846, -68.8535
  • Pituffik
W76.33N
  • 76.1538, -64.2165
  • Yngvar Nielsen Glacier
  • Mohn Glacier
W76.35N
  • 75.7416, -63.3988
  • Mohn Glacier
  • Gade Glacier
  • Meteor Bay
  • Yngvar Nielson Glacier
W76.40N
  • 76.0579, -65.9643
  • Savigssuaq Helland
  • Sidebriks
W76.45N
  • 76.1084, -67.6907
  • Dedodes
  • Harald Moltke
W77.55N
  • 77.0728, -66.2296
  • Leidy
  • Mane
  • Heilprin
  • Mellville
  • Tracy
W77.80N
  • 77.2407, -70.5337
  • Qaqortaq
  • Boudoin
W79.75N
  • 79.3702, -65.1597
  • Humboldt
W80.75N
  • 81.1505, -46.6109
  • Chow
S44.15W
  • 60.5845, -44.5380
  • unnamed glacier
S44.84W
  • 61.0923, -45.3465
  • Kiattuut Sermiat Glacier
  • Qooroq Fjord
S45.43W
  • 61.2196, -45.8994
  • Equlorutsit Kangigdlit
  • Sermia
S46.31W
  • 60.9223, -46.7905
  • Eqalorutsit Kangigdlit
  • Sermia West
S46.91W
  • 60.8876, -47.3303
  • Qaleragdlit
  • Naujat
  • Sermilik

Spatial Coverage Map

The spatial coverage map below shows the locations of all grids on a map of Greenland. A high resolution image of the map can be downloaded as a Portable Network Graphics (.png) file.  A shapefile of the spatial coverage image is also available.

Figure 1. Gridded Spatial Coverage Map

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Temporal Coverage

Data are available March 1985 through October 2016.

Temporal Resolution

Monthly

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Parameter or Variable

Parameter Description

This data set reports the following parameters:

  • Ice velocities (x- and y-components)
  • Error estimates (x- and y-components)

Corresponding ASCII text metadata files (.meta) are also provided and contain geographical information plus dates and codes that reveal the sensor combinations of the images used to create the monthly mean. The sensor combination key is provided in Table 3.

Table 3. Sensor Key for Metadata Files
Sensor Code
Landsat 8 OLI LC8
Landsat 7 ETM+ LE7
Landsat 5 TM LT5
Landsat 4 TM LT4
ASTER AST

The following sensor combinations are possible:  LT4/LT4, LT4/LT5, LT5/LT5, LT5/LE7, LT5/AST, LE7/LE7, LC8/LC8, LE7/LC8, AST/AST, LE7/AST, LC8/AST.

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Software and Tools

GeoTIFF files can be viewed with a variety of Geographical Information System (GIS) software packages including:

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Data Acquisition and Processing

Data Acquisition Methods

All Level-1 Landsat imagery was obtained from the U. S. Geological Survey (USGS | Landsat Level 1 Standard Data Products). ASTER (AST14DMO) imagery was obtained from the NASA Land Processes Distributed Active Archive Center (LPDAAC).

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Derivation Techniques and Algorithms

Processing Steps

These data were created using orthorectified Landsat Level L1T or L1G and ASTER (AST14DMO) imagery. Orthorectified images were received in UTM projection and converted to Polar Stereographic using Geographic Data Abstraction Library (GDAL) software. ASTER visible bands 1-3 were reduced to a single grayscale principle component image. The panchromatic band was used for Landsat 7 and 8. For Landsat 4 and 5 TM images, bands 2, 3, and 4 were reduced to a single grayscale principle component image. Velocity fields were constructed using images from the same sensor or combinations of Landsat 4, Landsat 5, Landsat 7, Landsat 8, and ASTER images. In most cases, only Landsat images from the same path/row were correlated to reduce the impact of terrain-dependent errors. To fill in temporal gaps in the 2016 coverage, cross path/row Landsat images were used. For these, the MEaSUREs Greenland Ice Mapping Project (GIMP) Digital Elevation Model from GeoEye and WorldView Imagery and orthorectifcation algorithm of Rosenau et al. (2012) were used.

Velocity fields were produced by an automated cross-correlation of sequential images using the Multi-Image Multi-Chip (MIMC) algorithm described in Ahn and Howat (2011) and updated in Jeong et al. (2017). The MIMC utilizes a range of image filters and search window sizes as well as both backward and forward matching to generate 64 matches per sample. Neighborhood statistics and an a priori velocity field, consisting of radar-derived velocities closest in time to the image dates from the MEaSUREs Greenland Ice Sheet Velocity Map from InSAR Data data set, were used to select the highest confidence solution and its uncertainty.

This velocity field was then corrected for image re-registration errors by subtracting the average displacement over bedrock or very slow moving ice (< 10 m/year), which is located using the a priori velocity field. The residual deviation of velocities over bedrock then provides the registration error (see Error Sources). Individual velocity image pairs within each region were sampled to the same grid and stacked into monthly medians at each grid point, providing a monthly sampling. The median error was also obtained.

Note: Monthly means are calculated from images, which may have acquisition dates from the preceding or succeeding month. For the naming convention, the month is determined from where the midpoint Julian dates fall. For example, September monthly means may have been generated from images that were acquired in August or in October but the midpoint Julian date between the images falls within September. The exact dates used are included in the meta file.

Error Sources

Uncertainty in the velocity solution results from uncertainty in the match solution and uncertainty in image co-registration. Match solution uncertainty is estimated at each grid point from the sample of individual velocity solutions that results from the MIMC procedure. This error is typically on the order of one-third of a pixel. Co-registration error, the dominant source of uncertainty, is estimated from the residual velocities obtained over bedrock and very slow ice after the mean is removed. These errors vary considerably, but are typically on the order of 100 m/year.

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Sensor or Instrument Description

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) obtains high-resolution (15 to 90 square meters per pixel) images of the Earth in 14 different wavelengths of the electromagnetic spectrum, ranging from visible to thermal infrared light. ASTER was launched in December 1999 onboard Terra, the flagship satellite of NASA's Earth Observing System (EOS). For more information, see Terra | ASTER.

The Enhanced Thematic Mapper Plus (ETM+) instrument on board Landsat 7 is a fixed “whisk-broom,” eight-band, multispectral scanning radiometer capable of providing high-resolution imaging information of the Earth’s surface. Orbiting at an altitude of 705 km, the instrument detects spectrally-filtered radiation in visible near-infrared, short-wave near-infrared, long-wave near-infrared, and panchromatic bands from the sun-lit Earth in a 183 km wide swath. Visit NASA Landsat Science | The Enhanced Thematic Mapper Plus for more information.

Onboard Landsat 4 and Landsat 5, the Thematic Mapper (TM) image data files consist of seven spectral bands (See band designations). The resolution is 30 meters for bands 1 to 7.  (Thermal infrared band 6 was collected at 120 meters, but was resampled to 30 meters. The approximate scene size is 170 km north-south by 183 km east-west (106 mi by 114 mi). See the Landsat Thematic Mapper Web site for more information.

The Operational Land Imager (OLI) on Landsat 8 is an enhanced version of Landsat 7’s ETM+ that adds two new spectral bands: a deep blue visible channel (band 1) specifically designed for water resources and coastal zone investigation; and a new infrared channel (band 9) to detect of cirrus clouds. For more information, see USGS | Landsat 8.

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Version History
Table 4. Version History
Version Description Effective Date
V2 (Update)
  • Temporal coverage expanded to 1985-2016 using data from Landsat 4 and 5
  • A more aggressive filtering method was applied to remove the following small, isolated clusters of data:
    • Ecoast-62.10N: OPT_E62.10N_2003-09, OPT_E62.10N_2003-10, OPT_E62.10N_2004-09, OPT_E62.10N_2004-10
    • Ecoast-64.65N: OPT_E64.65N_2011-09, OPT_E64.65N_2011-10
  • Spatial coverage was increased by 24 new grids
October 2017
V2 Changes for Version 2 include:
  • A correction was applied in the processing, which caused error values to appear as NaNs in some of the data
  • A more aggressive filtering method was applied to remove small, isolated clusters of data
  • Cross-path Landsat pairs were used to fill in temporal gaps in the 2016 data, using the MEaSUREs Greenland Ice Mapping Project (GIMP) Digital Elevation Model from GeoEye and WorldView Imagery and the orthorectifcation algorithm of Rosenau 2012
  • Spatial coverage was expanded to include include the Wcoast 80.75N grid
  • Temporal coverage was expanded from September 2015 to September 2016
  • To reduce overall size of the data set, GeoTIFFs are produced using Lempel–Ziv–Welch LZW lossless compression
May 2017
V1 Initial Release March 2016
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References and Related Publications

Contacts and Acknowledgments

Dr. Ian Howat
Ohio State University
Byrd Polar Research Center
Scott Hall Room 108
1090 Carmack Road
Columbus, Ohio 43210
USA

Acknowledgments: 

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

Document Information

DOCUMENT CREATION DATE

October 2017

No FAQs or How Tos available for this data set.

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