"""

This example code illustrates how to access and visualize an NSIDC 
ICESat-2 ATL06 version 4 L3A HDF5 file in Python.

If you have any questions, suggestions, or comments on this example, please use
the HDF-EOS Forum (http://hdfeos.org/forums).  If you would like to see an
example of any other NASA HDF/HDF-EOS data product that is not listed in the
HDF-EOS Comprehensive Examples page (http://hdfeos.org/zoo), feel free to
contact us at eoshelp@hdfgroup.org or post it at the HDF-EOS Forum
(http://hdfeos.org/forums).

Usage:  save this script and run

   $python ATL06_20190223232535_08780212_004_01.h5.py

The HDF5 file must in your current working directory.

Tested under: Python 3.9.1 :: Miniconda
Last updated: 2021-05-06
"""

import os
import matplotlib as mpl
import matplotlib.pyplot as plt
from mpl_toolkits.basemap import Basemap
import numpy as np

import h5py

FILE_NAME = 'ATL06_20190223232535_08780212_004_01.h5'
with h5py.File(FILE_NAME, mode='r') as f:

    # Ground Track L1
    latvar = f['/gt1l/land_ice_segments/latitude']
    latitude = latvar[:]
    
    lonvar = f['/gt1l/land_ice_segments/longitude']
    longitude = lonvar[:]
    
    # We'll plot land ice height.
    datavar = f['/gt1l/land_ice_segments/h_li']
    data = datavar[:]
    units = datavar.attrs['units']
    long_name = datavar.attrs['long_name']
    _FillValue = datavar.attrs['_FillValue']

    # Handle FillValue
    data[data == _FillValue] = np.nan
    data = np.ma.masked_where(np.isnan(data), data)    

    # Draw an equidistant cylindrical projection using the low resolution
    # coastline database.
    m = Basemap(projection='cyl', resolution='l',
                llcrnrlat=-90, urcrnrlat = 90,
                llcrnrlon=-180, urcrnrlon = 180)
    m.drawcoastlines(linewidth=0.5)
    m.drawparallels(np.arange(-90., 120., 30.))
    m.drawmeridians(np.arange(-180, 180., 45.))
    m.scatter(longitude, latitude, c=data, s=1, cmap=plt.cm.jet,
              edgecolors=None, linewidth=0)
    cb = m.colorbar()
    units = units.decode('ascii', 'replace')        
    cb.set_label(units)
    basename = os.path.basename(FILE_NAME)
    long_name = long_name.decode('ascii', 'replace')        
    plt.title('{0}\n{1}'.format(basename, long_name))
    
    fig = plt.gcf()    
    pngfile = "{0}.py.png".format(basename)
    fig.savefig(pngfile)