/**
* Returns the point which is a fraction along the line between 0 and 1.
*
* @param Point $point
* @param float $fraction between 0 and 1
*
* @throw \InvalidArgumentException
* @return Point
*/
public function getFractionAlongLineTo(Point $point, $fraction)
{
if ($fraction < 0 || $fraction > 1) {
throw new \InvalidArgumentException('$fraction must be between 0 and 1');
}
if (function_exists('fraction_along_gc_line') && Location::$useSpatialExtension) {
$result = fraction_along_gc_line($this->jsonSerialize(), $point->jsonSerialize(), $fraction);
return new self($result['coordinates']);
} else {
$distance = Location::haversine($this, $point);
$lat1 = $this->latitudeToRad();
$lat2 = $point->latitudeToRad();
$lon1 = $this->longitudeToRad();
$lon2 = $point->longitudeToRad();
$a = sin((1 - $fraction) * $distance) / sin($distance);
$b = sin($fraction * $distance) / sin($distance);
$x = $a * cos($lat1) * cos($lon1) + $b * cos($lat2) * cos($lon2);
$y = $a * cos($lat1) * sin($lon1) + $b * cos($lat2) * sin($lon2);
$z = $a * sin($lat1) + $b * sin($lat2);
$res_lat = atan2($z, sqrt(pow($x, 2) + pow($y, 2)));
$res_long = atan2($y, $x);
return new self(rad2deg($res_lat), rad2deg($res_long));
}
}
