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Data Set ID:
NSIDC-0593

MODIS Mosaic of Antarctica 2008-2009 (MOA2009) Image Map, Version 1

The MODIS Mosaic of Antarctica 2008-2009 (MOA2009) Image Map consists of two cloud-free digital image maps that show mean surface morphology and a quantitative measure of optical snow grain size on the Antarctic continent and surrounding islands using 260 orbit swaths from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on board the NASA EOS Aqua and Terra satellites.

Geographic Coverage

Spatial Coverage:
  • N: -60, S: -90, E: 180, W: -180

Spatial Resolution:
  • 250 m x 250 m
Temporal Coverage:
  • 1 November 2008 to 16 December 2008
  • 1 November 2008 to 28 February 2009
Temporal Resolution: Not specified
Parameter(s):
  • Glaciers/Ice Sheets > Firn > Snow Grain Size
  • Glaciers/Ice Sheets > Ice Sheets > Surface Morphology
Platform(s) AQUA, SATELLITES, TERRA
Sensor(s): MODIS
Data Format(s):
  • Binary
  • ENVI Vector File (.evf)
  • Generic Mapping Tools (.gmt)
  • ESRI Shapefile
  • Keyhole Markup Language (.kml)
  • GeoTIFF
  • ASCII Text
Version: V1
Data Contributor(s): Terry Haran, Jennifer Bohlander, Ted Scambos, Thomas Painter, Mark Fahnestock

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.

Haran, T., J. Bohlander, T. Scambos, T. Painter, and M. Fahnestock. 2014. MODIS Mosaic of Antarctica 2008-2009 (MOA2009) Image Map, Version 1. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: http://dx.doi.org/10.7265/N5KP8037. [Date Accessed].

Literature Citation

As a condition of using these data, we request that you acknowledge the author(s) of this data set by referencing the following peer-reviewed publication.

  • Scambos, T., T. Haran, M. Fahnestock, T. Painter, and J. Bohlander. 2007. MODIS-based Mosaic of Antarctica (MOA) Data Sets: Continent-wide Surface Morphology and Snow Grain Size, Remote Sensing of Environment. 111. 242-257. http://dx.doi.org/10.1016/j.rse.2006.12.020

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Detailed Data Description

NSIDC and the University of New Hampshire assembled a digital image map and snow-grain-size images of the Antarctic continent and surrounding islands called the MOA2009 Image Map. It provides a nearly-perfect cloud-free view of the ice sheet, ice shelves, and land surfaces. Two image data sets were compiled: a digitally smoothed red-light band 1 of MODIS image map, also called the MOA2009 Surface Morphology Image Map were the data were acquired 1 November 2008 through 28 February 2009; and two snow grain size images derived from normalized difference of calibrated band 1 and band 2 MODIS data, also called the MOA2009 Grain Size Image Map where the data were acquired 1 November 2008 through 28 February 2009, and the 2008 MOA Grain Size Image Map where the data were acquired 1 November 2008 through 16 December 2008.

Image data are available via FTP. Image data on the FTP site are provided as 16-bit images to preserve the radiometric content of the scenes.

Grain size cell values in the range of 10 through 1100 represent mean optical snow grain size in microns; values of 5 and 1105 represent grain size values outside this range, for example, some blue ice areas, or data for which a grain size could not be computed.

Format

The MOA2009 digital image maps are available at two spatial grid scales, 750 m and 125 m, and are provided as a gzipped flat binary 16-bit or 8-bit unsigned integer file (.img.gz) in little-endian byte order. Each .img.gz file has a corresponding gzipped GeoTiff (.tif.gz). file and a corresponding ENVI header file (img.hdr) in ASCII. Map projection parameter and grid parameter definition files (.mpp,.gpd) are also available.

Coastlines, ice sheet grounding lines, and islands are available in the following formats: shapefiles (.shp,.shx,.dbf,.prj), ENVI vector files (.evf); Generic Mapping Tools (.gmt), Keyhole Markup Language (.kml), and ASCII text files of point locations, with the exception of islands, which are not provided as a ASCII text file of point locations.

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File and Directory Structure

MOA2009 Image Maps

The image maps and ancillary files are located in the ftp://sidads.colorado.edu/pub/DATASETS/nsidc0593_moa2009/ directory. In this directory, there are three files: Moa0125.gpdMoa0750.gpd, and Moa.mpp; and three folders: envi, geotiff, and coastlines. The envi folder contains the .img.gz and .img.hdr files, the geotiff folder contains the .tif.gz files, and the coastlines folder contains the .shp,.shx,.dbf,.prj., .evf, .gmt, .kml, and .txt files. Refer to Table 2 for the list of available files.

Where:

Variable
Description
YYYY
Denotes the acquisition period for a given grain size file, where YYYY can equal either:
  • 2008 for 1 November 2008 through 16 December 2008
  • 2009 for 1 November 2008 through 28 February 2009.
*
Denotes that there are three format file extensions for each of these file types: .img.gz, .tif.gz, and .img.hdr.
Table 2. MOA2009 Image Maps and Ancillary Files
File Name
Description
00README.txt ASCII text file containing an abbreviated explanation of the data available for download
Moa.mpp Mapx Map Projection Parameters file
Moa0125.gpd Mapx Grid Parameter Definition file for 125 m grid
Moa0750.gpd Mapx Grid Parameter Definition file for 750 m grid
moa125_YYYY_grn_v1.1* 125 m weighted optical grain size image
16-bit unsigned integer little-endian flat binary
moa125_2009_hct_v1.1* 125 m count of MODIS scenes contributing to each moa125_2009_hp1 grid cell
8-bit unsigned integer flat binary.
moa125_2009_hp1_v1.1* 125 m high-pass band 1 surface morphology image
16-bit unsigned integer little-endian flat binary
moa125_2009_hwt_v1.1* 125 m average weight applied to computed hp1 values to determine composited moa125_2009_hp1 values
16-bit unsigned integer little-endian flat binary 
divide by 50000 to get true hwt decimal value.
moa750_YYYY_gct_v1.1* 750 m count of MODIS scenes contributing to each moa750_YYYY_grn grid cell
8-bit unsigned integer flat binary
moa750_YYYY_grn_v1.1* 750 m weighted optical grain size image
16-bit unsigned integer little-endian flat binary
moa750_YYYY_gsd_v1.1* 750 m standard deviation of unweighted optical grain size values contributing to each valid moa750_YYYY_gmn cell
16-bit unsigned integer little-endian flat binary
a value of 1 indicates there were less than two valid contributing unweighted grain size values
otherwise divide by 10 to get true gsd decimal value
moa750_YYYY_gwt_v1.1* 750 m average weight applied to computed grain size values to determine composited moa750_YYYY_grn values
16-bit unsigned integer little-endian flat binary
divide by 50000 to get true gwt decimal value
moa750_2009_hct_v1.1* 750 m count of MODIS scenes contributing to each moa750_2009_hp1 grid cell
8-bit unsigned integer flat binary.
moa750_2009_hp1_v1.1* 750 m high-pass band 1 surface morphology image
16-bit unsigned integer little-endian flat binary
moa750_2009_hwt_v1.1* 750 m average weight applied to computed hp1 values to determine composited moa750_YYYY_hp1 values
16-bit unsigned integer little-endian flat binary
divide by 50000 to get true hwt decimal value.
All moa125_* files were created directly from 250 meter resolution swath data that were gridded to 125 meter resolution.
Each moa750_...._g* file was created by resampling the corresponding 125 meter file using a nearest neighbor algorithm.
Each moa750_...._h* file was created by resampling the corresponding 125 meter file using a drop-in-the-bucket averaging alogithm.

Coastlines, Grounding Lines, and Islands

The Antarctic coastlines, ice sheet grounding lines, and island files were derived from the MOA2009 surface morphology image and are located in the ftp://sidads.colorado.edu/pub/DATASETS/nsidc0593_moa2009/ directory. Inside this directory, there is a coastlines folder. The coastlines folder contains the .shp, .shx, .dbf, .prj, .evf, .gmt, .kml, and .txt files. Refer to Table 3 for the list of available files.

Where:

Variable
Description
*

Denotes that there are up to eight format file extensions for each of these file types (coastlines, ice sheet grounding lines, and islands):

File Extension
Description
.txt ASCII text file containing WGS-84 latitude and longitude values.

Note: .txt files are only provided for the coastline and grounding line data,
not for the island data.
.evf ENVI vector files for the Antarctic islands, coastline, and grounding line.
.gmt Generic Mapping Tools Vector files for the Antarctic islands, coastline, and grounding line.
.kml Keyhole Markup Language file.
.dbf Shapefiles for the Antarctic islands, coastline, and grounding line.
.shx
.prj
.shp
Table 3. Antarctic Coastlines, Ice Sheet Grounding Lines, and Island Files
File Name Description
moa_2009_coastline_v1.1* Point locations for Antarctic coastline including ice shelf calving fronts.
moa_2009_groundingline_v1.1* Point locations for Antarctic grounding line.
moa_2009_islands_v1.1* Point locations for Antarctic island coastlines and ice-covered island grounding lines.
 
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File Size

The total size of the 750 m files is approximately 112 MB uncompressed.

The total size of the 125 m files is approximately 4 GB uncompressed.

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

The mosaic includes all land areas and islands south of 60° S that are larger than a few hundred meters. Land areas north of 60° S and areas of ocean more than a few tens of kilometers from coastlines are masked with zero-fill.

Spatial Resolution

The input swath data from MODIS Bands 1 and 2 have a nominal resolution of 250 m; however, MOA uses a super resolution or data cumulation image stacking scheme to increase the resolution of the final product beyond that of individual MODIS scenes. The estimated resolution of the final surface morphology composite ranges between 150 m and 250 m, depending on the number of images that were stacked and how the images were weighted. See Compositing the Image Swaths via Data Cumulation in the MAO2004 Guide Documentation for more details.

Projection Description

The 125 m grid images that make up the MOA2009 Image Map are provided in the Antarctic mapping projection recommended by the Scientific Committee on Antarctic Research (SCAR). This projection is identical to the Radarsat Antarctic Mapping Project Antarctic Mapping Mission 1 Synthetic Aperture Radar Image Mosaic of Antarctica, Version 2 data set with a 125 m mosaic.

  • Projection: Polar Stereographic
  • Spheroid: WGS-84
  • Longitude of Central Meridian: 0°
  • Latitude of True Scale: 71° S

Grid Description

Table 4 below lists the dimensions (in pixels) of the 125 m and 750 m product grids, and the location of the upper left corner of the upper left cell:

Table 4. Grid Dimensions
Dimension Grid (px) Upper left corner, upper left cell (m)
125 m 750 m
X 48333 8056 -3174450.0
y 41779 6964 2406325.0

Note: South Pole is not at the center of either of these grids.

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Temporal Coverage

Swaths for the surface morphology and full spring-summer snow grain images were acquired 1 November 2008 through 28 February 2009. The preferred spring-only grain size mosaic was constructed from images that were acquired 1 November 2008 through 16 December 2008.

Acquisition times were restricted to between 0500 GMT and 1330 GMT to ensure that the sun is positioned to the upper right of the projection grid in all scenes across the entire continent. To maintain a roughly uniform solar elevation angle across the composite, images acquired close to the austral summer solstice were selected for the region near the 135° W longitude coastline; for images near the 45° E longitude coastline, the majority of the scenes were acquired late January through February.

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Parameter or Variable

The MOA images report two parameters:

  • surface morphology, derived from brightness variations in MODIS Band 1 red light images;
  • snow grain size, inferred from the normalized difference radiance ratio of red to near-infrared light.

Surface Morphology

The surface morphology image required many processing steps, to create a seamless and uniform mosaic from the many images that were combined to generate single grid cell values. As such, the image values no longer have a clearly quantifiable relationship to the top-of-atmosphere, red light reflectances from which they were derived. Instead, the image provides a semi-quantitative but highly consistent representation of the surface shape and approximate reflectivity, as illuminated by the sun across all surface types for the entire continent.

Snow Grain Size

Pre-processing was reduced for the grain size mosaic. This approach sacrifices the seamlessness of the red-light image to produce a truer quantitative map of radiance ratios that can be used to approximate mean snow grain size in areas with dust-free, non-shadowed snow, firn, and ice.

The investigators derived lookup table values to correct for atmospheric effects and partially correct for Bi-directional Reflectance Distribution Function (BRDF) effects, using model runs of the Santa Barbara Discrete Ordinate Radiative Transfer (DISORT) Atmospheric Radiative Transfer (SBDART) software. The lookup tables were applied to image grids of radiance ratio and solar elevation to create images of snow optical grain size. These images were then composited to produce the final images using a similar weighting scheme to the surface morphology mosaic, favoring nadir-viewed scenes.

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Software and Tools

Visualizing the MOA2009 *.evf files require the use of ENVI 5.0+

You may also find the following resources and Web sites helpful when working with MOA:

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Data Acquisition and Processing

Theory of Measurements

See the Theory of Measurements section in the MOA2004 Guide Documentation.

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Data Acquisition Methods

See the Data Acquisition Methods section in the MOA2004 Guide Documentation.

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Derivation Techniques and Algorithms

Geolocation and Processing

See the Geolocation and Processing section in the MOA2004 Guide Documentation.

Destriping of MODIS Image Data

See the Destriping of MODIS Image Data section in the MOA2004 Guide Documentation.

Cloud Masking

See the Cloud Masking section in the MOA2004 Guide Documentation.

Compositing the Image Swaths via Data Cumulation

See the Compositing the Image Swaths via Data Cumulation section in the MOA2004 Guide Documentation.

High-Pass Filtered Surface Feature Composite

See the High-Pass Filtered Surface Feature Composite section in the MOA2004 Guide Documentation.

Optical Mean Snow Grain Size

See the Optical Mean Snow Grain Size section in the MOA2004 Guide Documentation.

Error Sources

See the Error Sources section in the MOA2004 Guide Documentation.

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Sensor or Instrument Description

See the Sensor or Instrument Description section in the MOA2004 Guide Documentation.

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References and Related Publications

Contacts and Acknowledgments

Ted Scambos
National Snow and Ice Data Center
449 UCB, University of Colorado
Boulder, CO 80309-0449 USA

Terry Haran
National Snow and Ice Data Center
449 UCB, University of Colorado
Boulder, CO 80309-0449 USA

Mark Fahnestock
Institute for the Study of Earth, Oceans, and Space
University of New Hampshire
Morse Hall
8 College Road
Durham, NH 03824-3525 USA

Thomas Painter
Jet Propulsion Laboratory
4800 Oak Grove Drive
Pasadena, CA 91109

Jennifer Bohlander
National Snow and Ice Data Center
449 UCB, University of Colorado
Boulder, CO 80309-0449 USA

Acknowledgements: 

This work was supported by NASA grant NNG04GM10G, and by USGS funds supporting J. Bohlander (instigated by J. Ferrigno) during image selection and cloud clearing. The investigators also wish to thank R. Bindschadler, W. Abdalati, and J. Ferrigno for their interest and support initiating this project.

Document Information

Document Creation Date

July 2014

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