/**
* Simplifies the given polyline
*
* 1. calculate the bearing angle between the first two points p1 and p2: b1
* 2. calculate the bearing angle between the next two points p2 and p3: b2
* 3. calculate the difference between b1 and b2: deltaB; if deltaB is
* smaller than the threshold angle, remove the middle point p2
* 4. start again at (1.) as long as the polyline contains more points
*
* @param Polyline $polyline
*
* @return Polyline
*/
public function simplify(Polyline $polyline)
{
$counterPoints = $polyline->getNumberOfPoints();
if ($counterPoints < 3) {
return clone $polyline;
}
$result = new Polyline();
$bearingCalc = new BearingEllipsoidal();
$points = $polyline->getPoints();
$index = 0;
// add the first point to the resulting polyline
$result->addPoint($points[$index]);
do {
$index++;
// preserve the last point of the original polyline
if ($index === $counterPoints - 1) {
$result->addPoint($points[$index]);
break;
}
$bearing1 = $bearingCalc->calculateBearing($points[$index - 1], $points[$index]);
$bearing2 = $bearingCalc->calculateBearing($points[$index], $points[$index + 1]);
$bearingDifference = min(fmod($bearing1 - $bearing2 + 360, 360), fmod($bearing2 - $bearing1 + 360, 360));
if ($bearingDifference > $this->bearingAngle) {
$result->addPoint($points[$index]);
}
} while ($index < $counterPoints);
return $result;
}
public function testIfCalculateFinalBearingWesternWorksAsExpected()
{
$point1 = new Coordinate(0, 0);
$point2 = new Coordinate(0, -10);
$bearingCalculator = new BearingEllipsoidal();
$this->assertEquals(270.0, $bearingCalculator->calculateFinalBearing($point1, $point2));
}
