/**
* Calculate the distance between two locations.
*
* Note, this is an estimate. The further the two places are from each other
* the less accurate the distance calculation will be. This method also assumes
* all locations are at the equator.
*/
public function distance(LocationInterface $location1, LocationInterface $location2)
{
$radLong1 = deg2rad($location1->longitude());
$radLat1 = deg2rad($location1->latitude());
$radLong2 = deg2rad($location2->longitude());
$radLat2 = deg2rad($location2->latitude());
$radius = $this->earthRadius(($location1->latitude() + $location2->latitude()) / 2);
$cosangle = cos($radLat1) * cos($radLat2) * (cos($radLong1) * cos($radLong2) + sin($radLong1) * sin($radLong2)) + sin($radLat1) * sin($radLat2);
return acos($cosangle) * $radius;
}
/**
* Calculate the distance between two locations.
*
* This uses Vincenty's formulae. For more information on this method
* see https://en.wikipedia.org/wiki/Vincenty's_formulae. There is also lots
* of good info at http://www.linz.govt.nz/geodetic/.
*
* Note, Vincenty's formulae is not known for its performance. It's more
* accurate than other methods but takes more processing time to calculate.
*/
public function distance(LocationInterface $location1, LocationInterface $location2)
{
$lat1 = deg2rad($location1->latitude());
$lat2 = deg2rad($location2->latitude());
$lon1 = deg2rad($location1->longitude());
$lon2 = deg2rad($location2->longitude());
// WGS-84 ellipsoid
$a = $this->earthRadiusSemimajor();
$b = $this->earthRadiusSemiminor();
$f = $this->earthFlattening();
$L = $lon2 - $lon1;
$U1 = atan((1 - $f) * tan($lat1));
$U2 = atan((1 - $f) * tan($lat2));
$sinU1 = sin($U1);
$cosU1 = cos($U1);
$sinU2 = sin($U2);
$cosU2 = cos($U2);
$lambda = $L;
$lambdaP = 2 * pi();
$iterLimit = 20;
while (abs($lambda - $lambdaP) > 1.0E-12 && --$iterLimit > 0) {
$sinLambda = sin($lambda);
$cosLambda = cos($lambda);
$sinSigma = sqrt($cosU2 * $sinLambda * ($cosU2 * $sinLambda) + ($cosU1 * $sinU2 - $sinU1 * $cosU2 * $cosLambda) * ($cosU1 * $sinU2 - $sinU1 * $cosU2 * $cosLambda));
if ($sinSigma == 0) {
return 0;
}
$cosSigma = $sinU1 * $sinU2 + $cosU1 * $cosU2 * $cosLambda;
$sigma = atan2($sinSigma, $cosSigma);
// was atan2
$alpha = asin($cosU1 * $cosU2 * $sinLambda / $sinSigma);
$cosSqAlpha = cos($alpha) * cos($alpha);
$cos2SigmaM = $cosSigma - 2 * $sinU1 * $sinU2 / $cosSqAlpha;
$C = $f / 16 * $cosSqAlpha * (4 + $f * (4 - 3 * $cosSqAlpha));
$lambdaP = $lambda;
$lambda = $L + (1 - $C) * $f * sin($alpha) * ($sigma + $C * $sinSigma * ($cos2SigmaM + $C * $cosSigma * (-1 + 2 * $cos2SigmaM * $cos2SigmaM)));
}
if ($iterLimit == 0) {
return FALSE;
// Oh no... we have a failure.
}
$uSq = $cosSqAlpha * ($a * $a - $b * $b) / ($b * $b);
$A = 1 + $uSq / 16384 * (4096 + $uSq * (-768 + $uSq * (320 - 175 * $uSq)));
$B = $uSq / 1024 * (256 + $uSq * (-128 + $uSq * (74 - 47 * $uSq)));
$deltaSigma = $B * $sinSigma * ($cos2SigmaM + $B / 4 * ($cosSigma * (-1 + 2 * $cos2SigmaM * $cos2SigmaM) - $B / 6 * $cos2SigmaM * (-3 + 4 * $sinSigma * $sinSigma) * (-3 + 4 * $cos2SigmaM * $cos2SigmaM)));
$s = $b * $A * ($sigma - $deltaSigma);
return round($s, 3);
// round to 1mm precision;
}
