This is a Javascript Google Maps v3 extension for the Polygon class to detect whether or not a point resides within it. Simplest Usage: var coordinate = new google.maps.LatLng(40, -90); var polygon = new google.maps.Polygon([], "#000000", 1, 1, "#336699", 0.3); var isWithinPolygon = polygon.containsLatLng(coordinate);