/**
* Convert a latitude, longitude height to x, y, z
* Formula for transformation is taken from OS document
* "A Guide to Coordinate Systems in Great Britain"
*
* @param LatLng $latLng
* @return Cartesian
*/
public static function fromLatLong(LatLng $latLng)
{
$a = $latLng->getRefEll()->getMaj();
$eSquared = $latLng->getRefEll()->getEcc();
$phi = deg2rad($latLng->getLat());
$lambda = deg2rad($latLng->getLng());
$v = $a / sqrt(1 - $eSquared * pow(sin($phi), 2));
$x = ($v + $latLng->getH()) * cos($phi) * cos($lambda);
$y = ($v + $latLng->getH()) * cos($phi) * sin($lambda);
$z = ((1 - $eSquared) * $v + $latLng->getH()) * sin($phi);
return new static($x, $y, $z, $latLng->getRefEll());
}
