已知两点经纬度，计算偏移角（正北为0，顺时针为正，逆时针为负）

function getAngle(preCoord,currCoord){
	var ret
     var w1 = preCoord.lat/180 * Math.PI
     var j1 = preCoord.lng/180 * Math.PI

     var w2 = currCoord.lat/180 * Math.PI
     var j2 = currCoord.lng/180 * Math.PI

     ret = 4 * Math.pow(Math.sin((w1 - w2) / 2), 2) - Math.pow(Math.sin((j1 - j2) / 2) * (Math.cos(w1) - Math.cos(w2)), 2);
     ret = Math.sqrt(ret);

     // var temp = Math.sin(Math.abs(j1 - j2) / 2) * (Math.cos(w1) + Math.cos(w2));
     var temp = Math.sin((j1 - j2) / 2) * (Math.cos(w1) + Math.cos(w2));
     // console.log(temp)
     ret = ret/temp;

     ret = Math.atan(ret) / Math.PI * 180 ;
     ret += 90;

     // 这里用如此臃肿的if..else是为了判定追踪单个点的具体情况,从而调整ret的值
     if(j1-j2 < 0){
         // console.log('j1<j2')
         if(w1-w2 < 0){
             // console.log('w1<w2')
             ret;
         }else{
             // console.log('w1>w2')
             ret = -ret+180;
         }
     }else{
         // console.log('j1>j2')
         if(w1-w2 < 0){
             // console.log('w1<w2')
             ret = 180+ret;
         }else{
             // console.log('w1>w2')
             ret = -ret;
         }
     }
     return ret ;
 }

本文地址：https://blog.csdn.net/weixin_43422861/article/details/107547804