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EASE-Grid Data

Data Sets in the Equal-Area Scalable Earth Grid

Versions

This page outlines the changes and known limitations associated with different versions of EASE-Grid. The original version of EASE-Grid was released in 1992 and the latest version, EASE-Grid 2.0, was defined in 2011. Table 1 summarizes the differences between the two versions.

Table 1. Comparison of EASE-Grid Versions
Feature Original EASE-Grid EASE-Grid 2.0
Projection ellipsoid International 1924 Authalic Sphere
WGS 84
Pole location Center of cell Intersection of center cells
Scale (data-set specific) Azimuthal/Cylindrical coupled (such as Nl/Sl/Ml 25.067525 km) Azimuthal: Exact (such as 25.0 km or 36.0 km)

Cylindrical: Integer-multiples across latitude of true scale
Dimensions Odd-numbered (721 x 721) Even-numbered (720 x 720)
Nested Grids Must choose between total coverage and nested cells Coverage can stay the same, only number of cells changes
Corner Points Corner cell locations in azimuthal grids are undefined No undefined corner cells
GeoTIFF Requires reprojection Supported without reprojection1
Software Issues Usually requires user to understand custom projection settings Most software supported1
1 Achieved by setting projection ellipsoid to reference datum


Software Support

Table 2 summarizes the current state of support for EASE-Grid format data when used with current popular software packages. Table 2 also lists geodetic parameter data set codes from the European Petroleum Survey Group (EPSG) for both the original EASE-Grid and 2.0 versions. EPSG codes are helpful shortcuts for PROJ.4 software, and for software that depends on PROJ.4, such as GDAL Tools.

Table 2. Current Software Support for EASE-Grid Versions, as of 17 January 2012
Software
& Codes
Original EASE-Grid
(Spherical Projection)
EASE-Grid 2.0
(WGS 84 Projection)
Current Status
HDFEOS 2.xx
HDFEOS 5.xx
Supported Cylindrical projection is supported. Azimuthal is not supported.
HDF depends on GCTP. NSIDC may propose a change to GCTP to support Lambert Azimuthal with ellipsoid.
PROJ.4 Supported Azimuthal and cylindrical EASE-Grid 2.0 supported in PROJ 4.8.0 (13 March 2012). Azimuthal projection was supported in PROJ 4.7.0 (23 September 2009). Bug in PROJ 4.7.0 resulted in error of ~15 km when transforming points near equator for cylindrical EASE-Grid 2.0 data. Both original EASE-Grid and EASE-Grid 2.0 are fully supported as of PROJ 4.8.0 (13 March 2012).
GDAL Tools Supported Supported, with correct version of PROJ.4. User must ensure correct PROJ.4 is installed; see PROJ.4 notes.
EPSG Codes North: 3408
South: 3409
Global: 3410
North: 3973
South: 3974
Global: 3975
PROJ 4.8.0 is required to obtain correct values for EASE-Grid 2.0 cylindrical.
ENVI Azimuthal supported.
T. Haran (NSIDC) has written procedure to add cylindrical equal-area to ENVI. Requires simple modifications to support header information for EASE-Grid data sets. ENVI cannot read/write user-defined projection information from/to GeoTIFF, but it can do so with its own ENVI header format.
Azimuthal supported.
Cylindrical equal-area requires user-defined projection information; simple modifications to support header information for EASE-Grid 2.0 data sets are forthcoming.
Simple modifications are required for cylindrical equal-area in both EASE-Grid versions; see respective column for current status.

Mapx Supported Supported N/A
ArcGIS Supported Supported N/A
ERDAS Supported Supported N/A

 

Page last updated: 2/11/14