NASA Distributed Active Archive Center (DAAC) at NSIDC

EASE-Grid Data

Data Sets in the Equal-Area Scalable Earth Grid

Ancillary Data

Several ancillary data sets are also available in the original EASE-Grid and in EASE-Grid 2.0. These data sets were derived from external data sources and then gridded to the EASE-Grid. These data sets help to answer questions such as what percentage of the EASE-Grid pixels are a particular type of land cover classification, and what is the average elevation at each EASE-Grid pixel. Choose one of the following categories to learn more and to download files:

See the EASE-Grid Geolocation Tools Web page for grids that contain latitudes and longitudes of EASE-Grid pixels, along with C, IDL, and Fortran subroutines for converting coordinates.

Land Cover

IGBP Land Cover Classification and LOCI Masks [top]

IGBP Land Cover Classification

These data provide land cover classifications derived from the Boston University MOD12Q1 V004 MODIS/Terra 1 km Land Cover Product. The data are available in various EASE-Grid and EASE-Grid 2.0 azimuthal and global projections, in multiple spatial resolutions ranging from 3 km to 100 km.

BU-MODIS Land-Ocean-Coast-Ice (LOCI) Masks

Corresponding Land-Ocean-Coast-Ice (LOCI) masks derived from the BU-MODIS land cover data are also available. These Land-Ocean-Coastline-Ice (LOCI) files provide land classification masks derived from the Boston University MOD12Q1 V004 MODIS/Terra 1 km Land Cover Product. The masks are available in various EASE-Grid and EASE-Grid 2.0 azimuthal and global projections, at various spatial resolutions ranging from 3 km to 100 km.

Global Land Cover Characterization (GLCC) Land Cover [top]

Table 3 lists the Global Land Cover Characterization (GLCC) data files in EASE-Grid. The IGBP land cover classes were used and are listed in Table 1.
 

Table 3. GLCC Land Cover Files
Region Resolution Grid size File Name
Northern Hemisphere 25 km 721 x 721 Nlglcc.tar
12.5 km 1441 x 1441 Nhglcc.tar
Southern Hemisphere 25 km 721 x 721 Slglcc.tar
12.5 km 1441 x 1441 Shglcc.tar
Global 25 km 1383 x 586 Mlglcc.tar
12.5 km 2766 x 1171 Mhglcc.tar

 

Each tar file contains a series of compressed flat data files for one projection and resolution. Each flat data file has the proportion of land per pixel for a single class stored as percent. For example, Nligbp01.dat is a 721 x 721 1-byte file (stored by row) where each byte represents the percent of land in that cell characterized as IGBP class 1. Pixels that are off the map or undefined in the original land cover map have a value of 255.

To extract a file, using water (class 17) from the 25 km Northern Hemisphere grid as an example, type the following command at a unix command prompt:

% tar xvf Nlglcc.tar

You will see the following output from this command:

x Nligbp01.dat.gz, 35579 bytes, 70 blocks
x Nligbp02.dat.gz, 22045 bytes, 44 blocks
x Nligbp03.dat.gz, 13565 bytes, 27 blocks
x Nligbp04.dat.gz, 26790 bytes, 53 blocks
x Nligbp05.dat.gz, 41744 bytes, 82 blocks
x Nligbp06.dat.gz, 24185 bytes, 48 blocks
x Nligbp07.dat.gz, 57880 bytes, 114 blocks
x Nligbp08.dat.gz, 50607 bytes, 99 blocks
x Nligbp09.dat.gz, 21303 bytes, 42 blocks
x Nligbp10.dat.gz, 50574 bytes, 99 blocks
x Nligbp11.dat.gz, 17230 bytes, 34 blocks
x Nligbp12.dat.gz, 62909 bytes, 123 blocks
x Nligbp13.dat.gz, 15851 bytes, 31 blocks
x Nligbp14.dat.gz, 63472 bytes, 124 blocks
x Nligbp15.dat.gz, 9178 bytes, 18 blocks
x Nligbp16.dat.gz, 43568 bytes, 86 blocks
x Nligbp17.dat.gz, 62126 bytes, 122 blocks

Then type:

% gzip -dv Nligbp17.dat.gz

You will see the following output from this command:

Nligbp17.dat.gz:        88.0% -- replaced with Nligbp17.dat

To acknowledge these EASE-Grid AVHRR land cover data in a publication, use the following citation:

Knowles, K. 2004. EASE-Grid Land Cover Data Resampled from AVHRR Global 1 km Land Cover, Version 2, March 1992 - April 1993. Boulder, Colorado USA: National Snow and Ice Data Center. Digital Media.

 


Elevations [top]

These are the Global Land One-km Base Elevation (GLOBE) data regridded to EASE-Grid. They consist of 2-byte integers in meters with values of -500 indicating no data. The .dat files have a big-endian, network byte order suitable for most Unix systems, including Sun and SGI. The .pc files have little-endian, host byte order suitable for Intel PC machines running Windows or Linux. Tables 4a and 4b provide links to the big-endian and little-endian files.

Table 4a. Big-Endian Byte Order Files
Hemisphere Resolution Grid size Download
Northern 25 km 721 x 721 Nlelev.dat
12.5 km 1441 x 1441 Nhelev.dat
Southern 25 km 721 x 721 Slelev.dat
12.5 km 1441 x 1441 Shelev.dat
Global 25 km 1383 x 586 Mlelev.dat
12.5 km 2766 x 1171 Mhelev.dat
Table 4b. Little-Endian Byte Order Files
Hemisphere Resolution Grid size Download
Northern 25 km 721 x 721 Nlelev.pc
12.5 km 1441 x 1441 Nhelev.pc
Southern 25 km 721 x 721 Slelev.pc
12.5 km 1441 x 1441 Shelev.pc
Global 25 km 1383 x 586 Mlelev.pc
12.5 km 2766 x 1171 Mhelev.pc

To acknowledge these EASE-Grid elevation data in a publication, use the following citation:

Knowles, K. 2001. EASE-Grid Elevation Data Resampled from the Global Land One-km Base Elevation (GLOBE) Project. Boulder, Colorado USA: National Snow and Ice Data Center. Digital media.


Pixel Area [top]

Data files are not provided because the EASE-Grids are based on equal-area map projections. Every pixel in a grid has the same area:

25 km grids (North, South, Global): 628.3827 sq km
12.5 km grids (North, South, Global): 157.0957 sq km