概述
最近遇到一个小问题：给定一个GPS坐标，判断是否在一个多边形区域内；查阅了一些资料，简单做一下记录。
算法(javascript)
ALon、ALat为需要判断的坐标点的经纬度，APoints为多边形顶点经纬度集合。
function isPtInPoly(ALon, ALat, APoints){
var iSum = 0, iCount;
var dLon1, dLon2, dLat1, dLat2, dLon;
if (APoints.length < 3) {
return false;
}
iCount = APoints.length;
for (var i = 0; i < iCount; i++) {
if (i == iCount - 1) {
dLon1 = APoints[i].longitude;
dLat1 = APoints[i].latitude;
dLon2 = APoints[0].longitude;
dLat2 = APoints[0].latitude;
} else {
dLon1 = APoints[i].longitude;
dLat1 = APoints[i].latitude;
dLon2 = APoints[i + 1].longitude;
dLat2 = APoints[i + 1].latitude;
}
//以下语句判断A点是否在边的两端点的水平平行线之间，在则可能有交点，开始判断交点是否在左射线上
if (((ALat >= dLat1) && (ALat < dLat2)) || ((ALat >= dLat2) && (ALat < dLat1))) {
if (Math.abs(dLat1 - dLat2) > 0) {
//得到 A点向左射线与边的交点的x坐标：
dLon = dLon1 - ((dLon1 - dLon2) * (dLat1 - ALat)) / (dLat1 - dLat2);
if (dLon < ALon)
iSum++;
}
}
}
if (iSum % 2 != 0) {
return true
}
return false
}
验证
借用高德地图进行验证：
- 进入高德地图某示例页面
- 将以下的代码复制到右侧的源代码编辑器中；
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="initial-scale=1.0, user-scalable=no, width=device-width">
<style>
html,
body,
#container {
width: 100%;
height: 100%;
}
</style>
<title>多边形的绘制和编辑</title>
<link rel="stylesheet" href="https://a.amap.com/jsapi_demos/static/demo-center/css/demo-center.css" />
<script src="https://webapi.amap.com/maps?v=1.4.15&key=您申请的key值&plugin=AMap.PolyEditor"></script>
<script src="https://a.amap.com/jsapi_demos/static/demo-center/js/demoutils.js"></script>
</head>
<body>
<div id="container"></div>
<div class="input-card" style="width: 120px">
<button class="btn" onclick="polyEditor.open()" style="margin-bottom: 5px">开始编辑</button>
<button class="btn" onclick="polyEditor.close()">结束编辑</button>
</div>
<script type="text/javascript">
// 绘制地图
var map = new AMap.Map("container", {
center: [120.73462,31.264536],
zoom: 16
});
// 多边形的几个顶点
var APoints = [
{'longitude': 120.7391550000, 'latitude': 31.2677060000},
{'longitude': 120.7280560000, 'latitude': 31.2640830000},
{'longitude': 120.7280270000, 'latitude': 31.2604840000},
{'longitude': 120.7404800000, 'latitude': 31.2644850000}
]
// 用多边形的几个顶点画多边形，数据和上面的那个是一样的
var path = [
[120.7391550000, 31.2677060000],
[120.7280560000, 31.2640830000],
[120.7280270000, 31.2604840000],
[120.7404800000, 31.2644850000],
[120.7391550000, 31.2677060000]
]
var polyline = new AMap.Polyline({
path: path,
strokeColor: 'red'
})
map.add(polyline)
// 设置点击事件，用于验证算法
map.on('click', function(e) {
alert(isPtInPoly(e.lnglat.getLng(), e.lnglat.getLat(), APoints))
});
function isPtInPoly(ALon, ALat, APoints){
var iSum = 0, iCount;
var dLon1, dLon2, dLat1, dLat2, dLon;
if (APoints.length < 3) {
return false;
}
iCount = APoints.length;
for (var i = 0; i < iCount; i++) {
if (i == iCount - 1) {
dLon1 = APoints[i].longitude;
dLat1 = APoints[i].latitude;
dLon2 = APoints[0].longitude;
dLat2 = APoints[0].latitude;
} else {
dLon1 = APoints[i].longitude;
dLat1 = APoints[i].latitude;
dLon2 = APoints[i + 1].longitude;
dLat2 = APoints[i + 1].latitude;
}
//以下语句判断A点是否在边的两端点的水平平行线之间，在则可能有交点，开始判断交点是否在左射线上
if (((ALat >= dLat1) && (ALat < dLat2)) || ((ALat >= dLat2) && (ALat < dLat1))) {
if (Math.abs(dLat1 - dLat2) > 0) {
//得到 A点向左射线与边的交点的x坐标：
dLon = dLon1 - ((dLon1 - dLon2) * (dLat1 - ALat)) / (dLat1 - dLat2);
if (dLon < ALon)
iSum++;
}
}
}
if (iSum % 2 != 0) {
return true
}
return false
}
</script>
</body>
</html>
-
然后，就可以在图上点击自由测试。
测试1
测试2
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