def _format_lat(self, lat):
        ''' Returned a formated latitude format for the file '''
        if self.ppd in [4, 16, 64, 128]:
            return None
        else:
            if lat < 0:
                return map(lambda x: "{0:0>2}"
                           .format(int(np.abs(x))) + 'S', self._map_center('lat', lat))
            else:
                return map(lambda x: "{0:0>2}"
                           .format(int(x)) + 'N', self._map_center('lat', lat))