Google Maps v3: check if point exists in polygon

Question

I am looking to find a way of checking if a point exists inside a polygon in Google Maps v3 (JavaScript). I\'ve searched everywhere and the only solutions I have found so fa

Answer 1

You have a very good example of containsLocation() method in Google Maps API documentation.

Answer 2

You should have a look about the Gmaps.js library. It has a quite simple method about geofence.

Answer 3

var coordinate = new google.maps.LatLng(0.457301,-0.597382);//replace with your lat and lng values
var isWithinPolygon = google.maps.geometry.poly.containsLocation(coordinate, yourPolygon);

Dont forget to include the library in your googleapis script. Read more...

<script src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&libraries=geometry"></script>

Answer 4

The example and implementation do not take into account that a polygon can cross the 180 degrees boundary.

The implementation does take it into account (implicitly) in the bounding box check, but the polygon check fails.

Answer 5

I have used the same thing and working fine and its offline code I have written this code in PHP you can write it any programming language.

class pointLocation {
    var $pointOnVertex = true; // Check if the point sits exactly on one of the vertices?

    function pointLocation() {
    }

    function pointInPolygon($point, $polygon, $pointOnVertex = true) {
        $this->pointOnVertex = $pointOnVertex;

        // Transform string coordinates into arrays with x and y values
        $point = $this->pointStringToCoordinates($point);
        $vertices = array(); 
        foreach ($polygon as $vertex) {
            $vertices[] = $this->pointStringToCoordinates($vertex); 
        }

        // Check if the point sits exactly on a vertex
        if ($this->pointOnVertex == true and $this->pointOnVertex($point, $vertices) == true) {
            return "vertex";
        }

        // Check if the point is inside the polygon or on the boundary
        $intersections = 0; 
        $vertices_count = count($vertices);

        for ($i=1; $i < $vertices_count; $i++) {
            $vertex1 = $vertices[$i-1]; 
            $vertex2 = $vertices[$i];
            if ($vertex1['y'] == $vertex2['y'] and $vertex1['y'] == $point['y'] and $point['x'] > min($vertex1['x'], $vertex2['x']) and $point['x'] < max($vertex1['x'], $vertex2['x'])) { // Check if point is on an horizontal polygon boundary
                return "boundary";
            }
            if ($point['y'] > min($vertex1['y'], $vertex2['y']) and $point['y'] <= max($vertex1['y'], $vertex2['y']) and $point['x'] <= max($vertex1['x'], $vertex2['x']) and $vertex1['y'] != $vertex2['y']) { 
                $xinters = ($point['y'] - $vertex1['y']) * ($vertex2['x'] - $vertex1['x']) / ($vertex2['y'] - $vertex1['y']) + $vertex1['x']; 
                if ($xinters == $point['x']) { // Check if point is on the polygon boundary (other than horizontal)
                    return "boundary";
                }
                if ($vertex1['x'] == $vertex2['x'] || $point['x'] <= $xinters) {
                    $intersections++; 
                }
            } 
        } 
        // If the number of edges we passed through is odd, then it's in the polygon. 
        if ($intersections % 2 != 0) {
            return "inside";
        } else {
            return "outside";
        }
    }

    function pointOnVertex($point, $vertices) {
        foreach($vertices as $vertex) {
            if ($point == $vertex) {
                return true;
            }
        }

    }

    function pointStringToCoordinates($pointString) {
        $coordinates = explode(" ", $pointString);
        return array("x" => $coordinates[0], "y" => $coordinates[1]);
    }

}

$pointLocation = new pointLocation();
$points = array("22.732965336387213 75.8609390258789");
$polygon = array("22.73549852921309 75.85424423217773","22.72346544538196 75.85561752319336","22.72346544538196 75.87175369262695","22.732332030848273 75.87295532226562","22.740406456758326 75.8686637878418","22.74198962160603 75.85407257080078");
echo '<pre>';
print_r($polygon);
// The last point's coordinates must be the same as the first one's, to "close the loop"
foreach($points as $key => $point) {
    echo "point " . ($key+1) . " ($point): " . $pointLocation->pointInPolygon($point, $polygon) . "<br>";
}

?>

Answer 6

One algorithm to solve this is ray-casting. See an explanation here.

And you can find code implementing this for the Google Maps JS API V3 here.

HTH.