public function toLatLng(Datum $datum)
{
$ellipsoid = $datum->getEllipsoid();
$e2 = ($ellipsoid->getA() * $ellipsoid->getA() - $ellipsoid->getB() * $ellipsoid->getB()) / ($ellipsoid->getA() * $ellipsoid->getA());
// 1st eccentricity squared
$G12 = ($ellipsoid->getA() * $ellipsoid->getA() - $ellipsoid->getB() * $ellipsoid->getB()) / ($ellipsoid->getB() * $ellipsoid->getB());
// 2nd eccentricity squared
$p = sqrt($this->x * $this->x + $this->y * $this->y);
// distance from minor axis
$R = sqrt($p * $p + $this->z + $this->z);
// parametric latitude (Bowring eqn 17, replacing tanβ = z·a / p·b)
$tan = $ellipsoid->getB() * $this->z / ($ellipsoid->getA() * $p) * (1 + $G12 * $ellipsoid->getB() / $R);
$sin = $tan / sqrt(1 + $tan * $tan);
$cos = $sin / $tan;
// geodetic latitude (Bowring eqn 18)
$G2 = atan2($this->z + $G12 * $ellipsoid->getB() * $sin * $sin * $sin, $p - $e2 * $ellipsoid->getA() * $cos * $cos * $cos);
// longitude
$G3 = atan2($this->y, $this->x);
return new LatLng(Misc::toDegrees($G2), Misc::toDegrees($G3), $datum);
}
