def METHOD_NAME(self, msg):
    """Get the area definition of the datasets in the file."""
    proj_param = msg.projparams.copy()
    Rx = 2 * np.arcsin(1. / msg['NrInRadiusOfEarth']) / msg['dx']
    Ry = 2 * np.arcsin(1. / msg['NrInRadiusOfEarth']) / msg['dy']
    x_0 = - msg['XpInGridLengths']
    x_1 = msg['Nx'] - msg['XpInGridLengths']
    y_0 = (msg['Ny'] - msg['YpInGridLengths']) * -1
    y_1 = msg['YpInGridLengths']
    min_x = (x_0 * Rx) * proj_param['h']
    max_x = (x_1 * Rx) * proj_param['h']
    min_y = (y_0 * Ry) * proj_param['h']
    max_y = (y_1 * Ry) * proj_param['h']
    area_extent = (min_x, min_y, max_x, max_y)
    area = geometry.AreaDefinition('hsaf_region',
                                   'A region from H-SAF',
                                   'geos',
                                   proj_param,
                                   msg['Nx'],
                                   msg['Ny'],
                                   area_extent)
    return area