String getFileName(double lat, double lon) {
        int lonInt = getMinLonForTile(lon);
        int latInt = getMinLatForTile(lat);
        return toLowerCase(getLatString(latInt) + getNorthString(latInt) + getLonString(lonInt) + getEastString(lonInt) + FILE_NAME_END);
    }
@Test
    public void testGetFileName() {
        assertEquals("30n000e_20101117_gmted_mea075", instance.getFileName(42.940339, 11.953125));
        assertEquals("30n090w_20101117_gmted_mea075", instance.getFileName(38.548165, -77.167969));
        assertEquals("70n180w_20101117_gmted_mea075", instance.getFileName(74.116047, -169.277344));
        assertEquals("70s180w_20101117_gmted_mea075", instance.getFileName(-61.015725, -156.621094));
        assertEquals("70n150e_20101117_gmted_mea075", instance.getFileName(74.590108, 166.640625));
        assertEquals("70s150e_20101117_gmted_mea075", instance.getFileName(-61.015725, 162.949219));
    }