Kerbin's diameter is 600 km, as compared to Earth's 6378.1 km Haversine, because Vincenty is only for the WGS84 Earth Spheroid Jeb lives at 45.74, -47.11 KSP is at -74.575277777778, -0.1025 'Point', 'coordinates' => [ 45.74, -47.11 ] ]; $ksp = [ 'type' => 'Point', 'coordinates' => [ -74.57527, -0.1025 ] ]; var_dump(haversine($jeb, $ksp, 600000)); ?>]]>