Tag Archives: EASE-2

Convert EASE-2 grid cell to latitude and longitude using Python

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The EASE-2 grid is used for a number of NASA datasets including SMAP. It is described in the following paper:

Brodzik, M. J., Billingsley, B., Haran, T., Raup, B., & Savoie, M. H. (2012). EASE-Grid 2.0: Incremental but Significant Improvements for Earth-Gridded Data Sets. ISPRS International Journal of Geo-Information, 1(3), 32–45. http://doi.org/10.3390/ijgi1010032

Files with the centre coordinate of each cell for EASE-2 grids at different resolutions are available from https://nsidc.org/data/ease/tools.html as well as tools for conversion.

To read these files into Python the following steps can be used:

  1. Download the relevant gridloc file.

    The FTP link for the grid location files is: ftp://sidads.colorado.edu/pub/tools/easegrid2/

    For this example I’ve chosen the 36km cylindrical EASE-2 grid (gridloc.EASE2_M36km.tgz)

  2. Un-tar using: 
    tar -xvf gridloc.EASE2_M36km.tgz
  3. Read the files into Python: 
    import numpy

# Read binary files and reshape to correct size
# The number of rows and columns are in the file name
lats = numpy.fromfile('EASE2_M36km.lats.964x406x1.double', 
                      dtype=numpy.float64).reshape((406,964))
lons = numpy.fromfile('EASE2_M36km.lons.964x406x1.double', 
                      dtype=numpy.float64).reshape((406,964))

# Extract latitude and longitude
# for a given row and column 
grid_row = 46
grid_column = 470

lat_val = lats[grid_row, grid_column]
lon_val = lons[grid_row, grid_column]