@Override
    String getFileName(double lat, double lon) {
        int intKey = calcIntKey(lat, lon);
        String str = areas.get(intKey);
        if (str == null)
            return null;

        int minLat = Math.abs(down(lat));
        int minLon = Math.abs(down(lon));
        str += "/";
        if (lat >= 0)
            str += "N";
        else
            str += "S";

        if (minLat < 10)
            str += "0";
        str += minLat;

        if (lon >= 0)
            str += "E";
        else
            str += "W";

        if (minLon < 10)
            str += "0";
        if (minLon < 100)
            str += "0";
        str += minLon;
        return str;
    }
@Disabled
    @Test
    public void testGetEleVerticalBorder() {
        instance = new SRTMProvider();
        // Border between the tiles N42E011 and N43E011
        assertEquals("Eurasia/N42E011", instance.getFileName(42.999999, 11.48));
        assertEquals(419, instance.getEle(42.999999, 11.48), precision);
        assertEquals("Eurasia/N43E011", instance.getFileName(43.000001, 11.48));
        assertEquals(419, instance.getEle(43.000001, 11.48), precision);
    }