def METHOD_NAME(self, fileName):
    """
    get a MeshDescriptor for the observation grid
    Parameters
    ----------
    fileName : str
        observation file name describing the source grid
    Returns
    -------
    obsDescriptor : ``MeshDescriptor``
        The descriptor for the observation grid
    """
    # Authors
    # -------
    # Darin Comeau, Xylar Asay-Davis
    # create a descriptor of the observation grid using the lat/lon
    # coordinates
    obsDescriptor = LatLonGridDescriptor.read(fileName=fileName,
                                              latVarName='latitude',
                                              lonVarName='longitude')
    return obsDescriptor