@Test
public void testDxy() throws Exception {

    final SynopticUncertaintyProvider separations = new SynopticUncertaintyProvider(SpatialResolution.DEGREE_5_00, null);
    assertEquals(188.815598, separations.dxy(0), 0.000001); // almost north pole
    assertEquals(286.830454, separations.dxy(18), 0.000001); // almost equator
    assertEquals(188.815598, separations.dxy(35), 0.000001); // almost south pole
    assertEquals(240.705816, separations.dxy(9), 0.000001);
    assertEquals(234.940236, separations.dxy(27), 0.000001);
}