/**
* testCalculateDestinationForBearingAndDistanceReturnsExpectedValue
*
* @param LatLong $latLong The starting point.
* @param float $bearing The initial bearing.
* @param float $distance The distance in metres to travel.
* @param LatLong $expected The expected destination.
*
* @dataProvider getLatLongWithInitialBearingDistanceAndDestination
*/
public function testCalculateDestinationForBearingAndDistanceReturnsExpectedValue(LatLong $latLong, $bearing, $distance, LatLong $expected)
{
$actual = $latLong->calculateDestinationForBearingAndDistance($bearing, $distance);
$tolerance = 0.3;
$this->assertEqualsWithinTolerance($expected->getLatitude(), $actual->getLatitude(), $tolerance);
$this->assertEqualsWithinTolerance($expected->getLongitude(), $actual->getLongitude(), $tolerance);
$this->assertEquals($latLong->getHeight(), $actual->getHeight());
// Height remains constant.
$this->assertEquals($expected->getDatum(), $actual->getDatum());
}
/**
* Calculate the distance in metres to another LatLong coordinate.
*
* This is a relatively expensive calculation to perform. It treats the Earth as an ellipsoid of the dimensions
* given for this LatLong's Datum's Ellipsoid so is more accurate than the Spherical law of cosines.
*
* @param LatLong $destination The coordinate to measure the distance to.
*
* @return float|null The distance in metres, or null if there was a problem.
*
* @throws InvalidArgumentException If the datum of this object does not match that of the $destination LatLong.
*/
public function calculateDistanceVincenty(LatLong $destination)
{
if ($destination->getDatum() != $this->datum) {
throw new InvalidArgumentException('Datums must match to calculate distance.');
}
$ellipsoid = $this->datum->getEllipsoid();
$a = $ellipsoid->getSemiMajorAxisMetres();
$b = $ellipsoid->getSemiMinorAxisMetres();
$f = $ellipsoid->getInverseFlattening();
$longDiffRad = deg2rad($destination->getLongitude() - $this->getLongitude());
$reducedLat = atan((1 - $f) * tan($this->getLatitudeRadians()));
$reducedLatDest = atan((1 - $f) * tan($destination->getLatitudeRadians()));
$sinReducedLat = sin($reducedLat);
$cosReducedLat = cos($reducedLat);
$sinReducedLatDest = sin($reducedLatDest);
$cosReducedLatDest = cos($reducedLatDest);
$lambda = $longDiffRad;
$maxIterations = 100;
do {
$sinLambda = sin($lambda);
$cosLambda = cos($lambda);
$sinSigma = sqrt(pow($cosReducedLatDest * $sinLambda, 2) + pow($cosReducedLat * $sinReducedLatDest - $sinReducedLat * $cosReducedLatDest * $cosLambda, 2));
// Return 0 if the points are coincident.
if ($sinSigma === 0.0) {
return 0.0;
}
$cosSigma = $sinReducedLat * $sinReducedLatDest + $cosReducedLat * $cosReducedLatDest * $cosLambda;
$sigma = atan2($sinSigma, $cosSigma);
$sinAlpha = $cosReducedLat * $cosReducedLatDest * $sinLambda / $sinSigma;
$cosSqAlpha = 1 - pow($sinAlpha, 2);
$cos2SigmaM = 0;
// At the equator, $cosSqAlpha === 0.
if ($cosSqAlpha !== 0) {
$cos2SigmaM = $cosSigma - 2 * $sinReducedLat * $sinReducedLatDest / $cosSqAlpha;
}
$c = $f / 16 * $cosSqAlpha * (4 + $f * (4 - 3 * $cosSqAlpha));
$lambdaP = $lambda;
$lambda = $longDiffRad + (1 - $c) * $f * $sinAlpha * ($sigma + $c * $sinSigma * ($cos2SigmaM + $c * $cosSigma * (-1 + 2 * $cos2SigmaM * $cos2SigmaM)));
} while (abs($lambda - $lambdaP) > '1e-12' && --$maxIterations > 0);
if ($maxIterations === 0) {
return null;
// Formula failed to converge.
}
$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 $s;
}
