def _check_invalid_longitudes(self):
        '''
        Checks to ensure that all longitudes are in the range -180. to 180
        '''
        idlon = self.strain.data['longitude'] > 180.
        if np.any(idlon):
            self.strain.data['longitude'][idlon] = \
                self.strain.data['longitude'][idlon] - 360.
Checks to ensure that all longitudes are in the range -180. to 180