如何检查多边形内是否存在纬度/经度坐标 - PHP

Question

我想用 PHP 编写一些代码来检查单个纬度/经度坐标与多边形的坐标。并返回真或假是否存在于多边形内。

例如我在这里创建了一个多边形.. http://www.geocodezip.com/polygonTool.asp

0: 53.34545,-6.255083 1：53.340121，-6.239033 2：53.338788，-6.238947 3：53.337405，-6.240492 4：53.334227，-6.245642 5：53.332074，-6.252937 6：53.330024，-6.264353 7：53.333766，-6.264868 8：53.33761，-6.265812 9：53.338583，-6.266155 10: 53.341607,-6.265383 11: 53.342683,-6.264439 12: 53.344067,-6.264696 13: 53.344733,-6.259632

我有一个用户位置... 53.338839, -6.249386（在这个多边形中确实存在）。

有没有一种简单的方法来验证它是在多边形内部还是外部？

Answer 1

确定一个点是否在多边形中的一种方法是计算从该点（在任何方向）绘制的线与多边形边界相交的次数。如果它们相交的次数为偶数次，则该点在外部。

以下 PHP 代码需要 2 个数组 $polyX = 多边形的经度点数组。重复第一个点以闭合多边形。 $polyy = 多边形的纬度点数组，

$polySides  = 13; //how many corners the polygon has
$polyX = array(53.34545,53.340121,53.338788,53.337405,53.334227,53.332074,53.330024,53.333766,53.33761,53.338583,53.341607,53.342683,53.344067,53.344733,53.34545);
$polyY = array(6.255083,-6.239033,-6.238947,-6.240492,-6.245642,-6.252937,-6.264353,-6.264868,-6.265812,-6.266155,-6.265383,-6.264439,-6.264696,-6.259632,6.255083);
$x =53.338839;//your coordinates
$y =-6.249386;


function pointInPolygon($polySides,$polyX,$polyY,$x,$y) {
  $j = $polySides-1 ;
  $oddNodes = 0;
  for ($i=0; $i<$polySides; $i++) {
    if ($polyY[$i]<$y && $polyY[$j]>=$y 
 ||  $polyY[$j]<$y && $polyY[$i]>=$y) {
    if ($polyX[$i]+($y-$polyY[$i])/($polyY[$j]-$polyY[$i])*($polyX[$j]-$polyX[$i])<$x)    {
    $oddNodes=!$oddNodes; }}
   $j=$i; }

  return $oddNodes; }


 if (pointInPolygon($polySides,$polyX,$polyY,$x,$y)){
  echo "Is in polygon!";
}
else echo "Is not in polygon";

请参阅 this 了解 JavaScript 实现。

Answer 2

来自我的Geodetic classes，基本功能是：

function isInRegion(Geodetic_LatLong $position)
{
    $latitude = $position->getLatitude()->getValue();
    $longitude = $position->getLongitude()->getValue();
    $perimeterNodeCount = count($this->_nodePoints);
    $jIndex = $perimeterNodeCount - 1 ;
    $oddNodes = FALSE;
    for ($iIndex = 0; $iIndex < $perimeterNodeCount; ++$iIndex) {
        $iLatitude = $this->_nodePoints[$iIndex]->getLatitude()->getValue();
        $jLatitude = $this->_nodePoints[$jIndex]->getLatitude()->getValue();
        if (($iLatitude < $latitude && $jLatitude >= $latitude) ||
            ($jLatitude < $latitude && $iLatitude >= $latitude)) {
            $iLongitude = $this->_nodePoints[$iIndex]->getLongitude()->getValue();
            $jLongitude = $this->_nodePoints[$jIndex]->getLongitude()->getValue();
            if ($iLongitude +
                ($latitude - $iLatitude) /
                ($jLatitude - $iLatitude) * ($jLongitude - $iLongitude) < $longitude) {
                $oddNodes = !$oddNodes;
            }
        }
        $jIndex = $iIndex;
    }
    return $oddNodes;
}