地球坐标系转为百度坐标系

因项目需要，现在已有的是天地图的经纬度数据，即地球坐标系，也称WGS-84

业务需求需要判断某个点的经纬度是否在某个面里，天地图不支持对应的API，然后在百度里找到了一个

BMapLib.GeoUtils.isPointInPolygon

这个方法需要提前引入js库

<script src="./js/GeoUtils.js"></script>

GeoUtils.js具体代码如下，直接拷贝保存即可

/**
 * @fileoverview GeoUtils类提供若干几何算法，用来帮助用户判断点与矩形、
 * 圆形、多边形线、多边形面的关系,并提供计算折线长度和多边形的面积的公式。 
 * 主入口类是<a href="symbols/BMapLib.GeoUtils.html">GeoUtils</a>，
 * 基于Baidu Map API 1.2。
 *
 * @author Baidu Map Api Group 
 * @version 1.2
 */

/** 
 * @namespace BMap的所有library类均放在BMapLib命名空间下
 */
var BMapLib = window.BMapLib = BMapLib || {};
(function() { 
    
    /**
     * 地球半径
     */
    var EARTHRADIUS = 6370996.81; 

    /** 
     * @exports GeoUtils as BMapLib.GeoUtils 
     */
    var GeoUtils =
    /**
     * GeoUtils类，静态类，勿需实例化即可使用
     * @class GeoUtils类的<b>入口</b>。
     * 该类提供的都是静态方法，勿需实例化即可使用。     
     */
    BMapLib.GeoUtils = function(){
        
    }
    
    /**
     * 判断点是否在矩形内
     * @param {Point} point 点对象
     * @param {Bounds} bounds 矩形边界对象
     * @returns {Boolean} 点在矩形内返回true,否则返回false
     */
    GeoUtils.isPointInRect = function(point, bounds){
        //检查类型是否正确
        if (!(point instanceof BMap.Point) || 
            !(bounds instanceof BMap.Bounds)) {
            return false;
        }
        var sw = bounds.getSouthWest(); //西南脚点
        var ne = bounds.getNorthEast(); //东北脚点
        return (point.lng >= sw.lng && point.lng <= ne.lng && point.lat >= sw.lat && point.lat <= ne.lat);
    }
    
    /**
     * 判断点是否在圆形内
     * @param {Point} point 点对象
     * @param {Circle} circle 圆形对象
     * @returns {Boolean} 点在圆形内返回true,否则返回false
     */
    GeoUtils.isPointInCircle = function(point, circle){
        //检查类型是否正确
        if (!(point instanceof BMap.Point) || 
            !(circle instanceof BMap.Circle)) {
            return false;
        }

        //point与圆心距离小于圆形半径，则点在圆内，否则在圆外
        var c = circle.getCenter();
        var r = circle.getRadius();

        var dis = GeoUtils.getDistance(point, c);
        if(dis <= r){
            return true;
        } else {
            return false;
        }
    }
    
    /**
     * 判断点是否在折线上
     * @param {Point} point 点对象
     * @param {Polyline} polyline 折线对象
     * @returns {Boolean} 点在折线上返回true,否则返回false
     */
    GeoUtils.isPointOnPolyline = function(point, polyline){
        //检查类型
        if(!(point instanceof BMap.Point) ||
            !(polyline instanceof BMap.Polyline)){
            return false;
        }

        //首先判断点是否在线的外包矩形内，如果在，则进一步判断，否则返回false
        var lineBounds = polyline.getBounds();
        if(!this.isPointInRect(point, lineBounds)){
            return false;
        }

        //判断点是否在线段上，设点为Q，线段为P1P2 ，
        //判断点Q在该线段上的依据是：( Q - P1 ) × ( P2 - P1 ) = 0，且 Q 在以 P1，P2为对角顶点的矩形内
        var pts = polyline.getPath();
        for(var i = 0; i < pts.length - 1; i++){
            var curPt = pts[i];
            var nextPt = pts[i + 1];
            //首先判断point是否在curPt和nextPt之间，即：此判断该点是否在该线段的外包矩形内
            if (point.lng >= Math.min(curPt.lng, nextPt.lng) && point.lng <= Math.max(curPt.lng, nextPt.lng) &&
                point.lat >= Math.min(curPt.lat, nextPt.lat) && point.lat <= Math.max(curPt.lat, nextPt.lat)){
                //判断点是否在直线上公式
                var precision = (curPt.lng - point.lng) * (nextPt.lat - point.lat) - 
                    (nextPt.lng - point.lng) * (curPt.lat - point.lat);                
                if(precision < 2e-10 && precision > -2e-10){//实质判断是否接近0
                    return true;
                }                
            }
        }
        
        return false;
    }
    
    /**
     * 判断点是否多边形内
     * @param {Point} point 点对象
     * @param {Polyline} polygon 多边形对象
     * @returns {Boolean} 点在多边形内返回true,否则返回false
     */
    GeoUtils.isPointInPolygon = function(point, polygon){
        //检查类型
        if(!(point instanceof BMap.Point) ||
            !(polygon instanceof BMap.Polygon)){
            return false;
        }

        //首先判断点是否在多边形的外包矩形内，如果在，则进一步判断，否则返回false
        var polygonBounds = polygon.getBounds();
        if(!this.isPointInRect(point, polygonBounds)){
            return false;
        }

        var pts = polygon.getPath();//获取多边形点
        
        //下述代码来源：http://paulbourke.net/geometry/insidepoly/，进行了部分修改
        //基本思想是利用射线法，计算射线与多边形各边的交点，如果是偶数，则点在多边形外，否则
        //在多边形内。还会考虑一些特殊情况，如点在多边形顶点上，点在多边形边上等特殊情况。
        
        var N = pts.length;
        var boundOrVertex = true; //如果点位于多边形的顶点或边上，也算做点在多边形内，直接返回true
        var intersectCount = 0;//cross points count of x 
        var precision = 2e-10; //浮点类型计算时候与0比较时候的容差
        var p1, p2;//neighbour bound vertices
        var p = point; //测试点
        
        p1 = pts[0];//left vertex        
        for(var i = 1; i <= N; ++i){//check all rays            
            if(p.equals(p1)){
                return boundOrVertex;//p is an vertex
            }
            
            p2 = pts[i % N];//right vertex            
            if(p.lat < Math.min(p1.lat, p2.lat) || p.lat > Math.max(p1.lat, p2.lat)){//ray is outside of our interests                
                p1 = p2; 
                continue;//next ray left point
            }
            
            if(p.lat > Math.min(p1.lat, p2.lat) && p.lat < Math.max(p1.lat, p2.lat)){//ray is crossing over by the algorithm (common part of)
                if(p.lng <= Math.max(p1.lng, p2.lng)){//x is before of ray                    
                    if(p1.lat == p2.lat && p.lng >= Math.min(p1.lng, p2.lng)){//overlies on a horizontal ray
                        return boundOrVertex;
                    }
                    
                    if(p1.lng == p2.lng){//ray is vertical                        
                        if(p1.lng == p.lng){//overlies on a vertical ray
                            return boundOrVertex;
                        }else{//before ray
                            ++intersectCount;
                        } 
                    }else{//cross point on the left side                        
                        var xinters = (p.lat - p1.lat) * (p2.lng - p1.lng) / (p2.lat - p1.lat) + p1.lng;//cross point of lng                        
                        if(Math.abs(p.lng - xinters) < precision){//overlies on a ray
                            return boundOrVertex;
                        }
                        
                        if(p.lng < xinters){//before ray
                            ++intersectCount;
                        } 
                    }
                }
            }else{//special case when ray is crossing through the vertex                
                if(p.lat == p2.lat && p.lng <= p2.lng){//p crossing over p2                    
                    var p3 = pts[(i+1) % N]; //next vertex                    
                    if(p.lat >= Math.min(p1.lat, p3.lat) && p.lat <= Math.max(p1.lat, p3.lat)){//p.lat lies between p1.lat & p3.lat
                        ++intersectCount;
                    }else{
                        intersectCount += 2;
                    }
                }
            }            
            p1 = p2;//next ray left point
        }
        
        if(intersectCount % 2 == 0){//偶数在多边形外
            return false;
        } else { //奇数在多边形内
            return true;
        }            
    }

    /**
     * 将度转化为弧度
     * @param {degree} Number 度     
     * @returns {Number} 弧度
     */
    GeoUtils.degreeToRad =  function(degree){
        return Math.PI * degree/180;    
    }
    
    /**
     * 将弧度转化为度
     * @param {radian} Number 弧度     
     * @returns {Number} 度
     */
    GeoUtils.radToDegree = function(rad){
        return (180 * rad) / Math.PI;       
    }
    
    /**
     * 将v值限定在a,b之间，纬度使用
     */
    function _getRange(v, a, b){
        if(a != null){
          v = Math.max(v, a);
        }
        if(b != null){
          v = Math.min(v, b);
        }
        return v;
    }
    
    /**
     * 将v值限定在a,b之间，经度使用
     */
    function _getLoop(v, a, b){
        while( v > b){
          v -= b - a
        }
        while(v < a){
          v += b - a
        }
        return v;
    }

    /**
     * 计算两点之间的距离,两点坐标必须为经纬度
     * @param {point1} Point 点对象
     * @param {point2} Point 点对象
     * @returns {Number} 两点之间距离，单位为米
     */
    GeoUtils.getDistance = function(point1, point2){
        //判断类型
        if(!(point1 instanceof BMap.Point) ||
            !(point2 instanceof BMap.Point)){
            return 0;
        }

        point1.lng = _getLoop(point1.lng, -180, 180);
        point1.lat = _getRange(point1.lat, -74, 74);
        point2.lng = _getLoop(point2.lng, -180, 180);
        point2.lat = _getRange(point2.lat, -74, 74);
        
        var x1, x2, y1, y2;
        x1 = GeoUtils.degreeToRad(point1.lng);
        y1 = GeoUtils.degreeToRad(point1.lat);
        x2 = GeoUtils.degreeToRad(point2.lng);
        y2 = GeoUtils.degreeToRad(point2.lat);

        return EARTHRADIUS * Math.acos((Math.sin(y1) * Math.sin(y2) + Math.cos(y1) * Math.cos(y2) * Math.cos(x2 - x1)));    
    }
    
    /**
     * 计算折线或者点数组的长度
     * @param {Polyline|Array<Point>} polyline 折线对象或者点数组
     * @returns {Number} 折线或点数组对应的长度
     */
    GeoUtils.getPolylineDistance = function(polyline){
        //检查类型
        if(polyline instanceof BMap.Polyline || 
            polyline instanceof Array){
            //将polyline统一为数组
            var pts;
            if(polyline instanceof BMap.Polyline){
                pts = polyline.getPath();
            } else {
                pts = polyline;
            }
            
            if(pts.length < 2){//小于2个点，返回0
                return 0;
            }

            //遍历所有线段将其相加，计算整条线段的长度
            var totalDis = 0;
            for(var i =0; i < pts.length - 1; i++){
                var curPt = pts[i];
                var nextPt = pts[i + 1]
                var dis = GeoUtils.getDistance(curPt, nextPt);
                totalDis += dis;
            }

            return totalDis;
            
        } else {
            return 0;
        }
    }
    
    /**
     * 计算多边形面或点数组构建图形的面积,注意：坐标类型只能是经纬度，且不适合计算自相交多边形的面积
     * @param {Polygon|Array<Point>} polygon 多边形面对象或者点数组
     * @returns {Number} 多边形面或点数组构成图形的面积
     */
    GeoUtils.getPolygonArea = function(polygon){
        //检查类型
        if(!(polygon instanceof BMap.Polygon) &&
            !(polygon instanceof Array)){
            return 0;
        }
        var pts;
        if(polygon instanceof BMap.Polygon){
            pts = polygon.getPath();
        }else{
            pts = polygon;    
        }
        
        if(pts.length < 3){//小于3个顶点，不能构建面
            return 0;
        }
        
        var totalArea = 0;//初始化总面积
        var LowX = 0.0;
        var LowY = 0.0;
        var MiddleX = 0.0;
        var MiddleY = 0.0;
        var HighX = 0.0;
        var HighY = 0.0;
        var AM = 0.0;
        var BM = 0.0;
        var CM = 0.0;
        var AL = 0.0;
        var BL = 0.0;
        var CL = 0.0;
        var AH = 0.0;
        var BH = 0.0;
        var CH = 0.0;
        var CoefficientL = 0.0;
        var CoefficientH = 0.0;
        var ALtangent = 0.0;
        var BLtangent = 0.0;
        var CLtangent = 0.0;
        var AHtangent = 0.0;
        var BHtangent = 0.0;
        var CHtangent = 0.0;
        var ANormalLine = 0.0;
        var BNormalLine = 0.0;
        var CNormalLine = 0.0;
        var OrientationValue = 0.0;
        var AngleCos = 0.0;
        var Sum1 = 0.0;
        var Sum2 = 0.0;
        var Count2 = 0;
        var Count1 = 0;
        var Sum = 0.0;
        var Radius = EARTHRADIUS; //6378137.0,WGS84椭球半径 
        var Count = pts.length;        
        for (var i = 0; i < Count; i++) {
            if (i == 0) {
                LowX = pts[Count - 1].lng * Math.PI / 180;
                LowY = pts[Count - 1].lat * Math.PI / 180;
                MiddleX = pts[0].lng * Math.PI / 180;
                MiddleY = pts[0].lat * Math.PI / 180;
                HighX = pts[1].lng * Math.PI / 180;
                HighY = pts[1].lat * Math.PI / 180;
            }
            else if (i == Count - 1) {
                LowX = pts[Count - 2].lng * Math.PI / 180;
                LowY = pts[Count - 2].lat * Math.PI / 180;
                MiddleX = pts[Count - 1].lng * Math.PI / 180;
                MiddleY = pts[Count - 1].lat * Math.PI / 180;
                HighX = pts[0].lng * Math.PI / 180;
                HighY = pts[0].lat * Math.PI / 180;
            }
            else {
                LowX = pts[i - 1].lng * Math.PI / 180;
                LowY = pts[i - 1].lat * Math.PI / 180;
                MiddleX = pts[i].lng * Math.PI / 180;
                MiddleY = pts[i].lat * Math.PI / 180;
                HighX = pts[i + 1].lng * Math.PI / 180;
                HighY = pts[i + 1].lat * Math.PI / 180;
            }
            AM = Math.cos(MiddleY) * Math.cos(MiddleX);
            BM = Math.cos(MiddleY) * Math.sin(MiddleX);
            CM = Math.sin(MiddleY);
            AL = Math.cos(LowY) * Math.cos(LowX);
            BL = Math.cos(LowY) * Math.sin(LowX);
            CL = Math.sin(LowY);
            AH = Math.cos(HighY) * Math.cos(HighX);
            BH = Math.cos(HighY) * Math.sin(HighX);
            CH = Math.sin(HighY);
            CoefficientL = (AM * AM + BM * BM + CM * CM) / (AM * AL + BM * BL + CM * CL);
            CoefficientH = (AM * AM + BM * BM + CM * CM) / (AM * AH + BM * BH + CM * CH);
            ALtangent = CoefficientL * AL - AM;
            BLtangent = CoefficientL * BL - BM;
            CLtangent = CoefficientL * CL - CM;
            AHtangent = CoefficientH * AH - AM;
            BHtangent = CoefficientH * BH - BM;
            CHtangent = CoefficientH * CH - CM;
            AngleCos = (AHtangent * ALtangent + BHtangent * BLtangent + CHtangent * CLtangent) / (Math.sqrt(AHtangent * AHtangent + BHtangent * BHtangent + CHtangent * CHtangent) * Math.sqrt(ALtangent * ALtangent + BLtangent * BLtangent + CLtangent * CLtangent));
            AngleCos = Math.acos(AngleCos);            
            ANormalLine = BHtangent * CLtangent - CHtangent * BLtangent;
            BNormalLine = 0 - (AHtangent * CLtangent - CHtangent * ALtangent);
            CNormalLine = AHtangent * BLtangent - BHtangent * ALtangent;
            if (AM != 0)
                OrientationValue = ANormalLine / AM;
            else if (BM != 0)
                OrientationValue = BNormalLine / BM;
            else
                OrientationValue = CNormalLine / CM;
            if (OrientationValue > 0) {
                Sum1 += AngleCos;
                Count1++;
            }
            else {
                Sum2 += AngleCos;
                Count2++;
            }
        }        
        var tempSum1, tempSum2;
        tempSum1 = Sum1 + (2 * Math.PI * Count2 - Sum2);
        tempSum2 = (2 * Math.PI * Count1 - Sum1) + Sum2;
        if (Sum1 > Sum2) {
            if ((tempSum1 - (Count - 2) * Math.PI) < 1)
                Sum = tempSum1;
            else
                Sum = tempSum2;
        }
        else {
            if ((tempSum2 - (Count - 2) * Math.PI) < 1)
                Sum = tempSum2;
            else
                Sum = tempSum1;
        }
        totalArea = (Sum - (Count - 2) * Math.PI) * Radius * Radius;

        return totalArea; //返回总面积
    }
   
})();//闭包结束

然后有了这个方法以后，真正的技术难题是如何把地球坐标系的经纬度转为百度坐标系，坐标转换具体原因可自行百度查阅。

最后经过千辛万苦，终于在一位大佬的博文里看到了曲线救国的方法

先把地球坐标系转为火星坐标系，再把火星坐标系转为百度坐标系，虽然麻烦一些，但是总归完成了效果

具体代码如下 

tips

outOfChina方法中

原博文里的lat和lon顺序反了，这里特此纠正

function transformWDS2BD (nowlat, nowlon) {
    // 地球坐标系(WGS-84)转火星坐标系(GCJ)
    var pi = 3.14159265358979324;
    var a = 6378245.0;
    var ee = 0.00669342162296594323;
    /*判断是否在国内，不在国内则不做偏移*/
　　function outOfChina(lat, lon) 

    {
        if ((lon < 72.004 || lon > 137.8347)&&(lat < 0.8293 || lat > 55.8271)){
            return true;
        }else {
            return false;
        }
    }
    function transformLat(x,y)
    {
        var ret = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * Math.sqrt(Math.abs(x));
        ret += (20.0 * Math.sin(6.0 * x * pi) + 20.0 * Math.sin(2.0 * x * pi)) * 2.0 / 3.0;
        ret += (20.0 * Math.sin(y * pi) + 40.0 * Math.sin(y / 3.0 * pi)) * 2.0 / 3.0;
        ret += (160.0 * Math.sin(y / 12.0 * pi) + 320 * Math.sin(y * pi / 30.0)) * 2.0 / 3.0;
        return ret;
    }

    function transformLon(x,y)
    {
        var ret = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * Math.sqrt(Math.abs(x));
        ret += (20.0 * Math.sin(6.0 * x * pi) + 20.0 * Math.sin(2.0 * x * pi)) * 2.0 / 3.0;
        ret += (20.0 * Math.sin(x * pi) + 40.0 * Math.sin(x / 3.0 * pi)) * 2.0 / 3.0;
        ret += (150.0 * Math.sin(x / 12.0 * pi) + 300.0 * Math.sin(x / 30.0 * pi)) * 2.0 / 3.0;
        return ret;
    }

    function transform(wgLat,wgLon)
    {
        var mars_point={lon:0,lat:0};
        if (outOfChina(wgLat, wgLon))
        {
            mars_point.lat = wgLat;
            mars_point.lon = wgLon;
            return mars_point;
        }
        var dLat = transformLat(wgLon - 105.0, wgLat - 35.0);
        var dLon = transformLon(wgLon - 105.0, wgLat - 35.0);
        var radLat = wgLat / 180.0 * pi;
        var magic = Math.sin(radLat);
        magic = 1 - ee * magic * magic;
        var sqrtMagic = Math.sqrt(magic);
        dLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * pi);
        dLon = (dLon * 180.0) / (a / sqrtMagic * Math.cos(radLat) * pi);
        mars_point.lat = wgLat + dLat;
        mars_point.lon = wgLon + dLon;
        return mars_point
    }
  // 火星坐标转百度坐标
  var x_pi=3.14159265358979324 * 3000.0 / 180.0;
  function marsTobaidu(mars_point){
      var baidu_point={lon:0,lat:0};
      var x=mars_point.lon;
      var y=mars_point.lat;
      var z = Math.sqrt(x * x + y * y) + 0.00002 * Math.sin(y * x_pi);
      var theta = Math.atan2(y, x) + 0.000003 * Math.cos(x * x_pi);
      baidu_point.lon = z * Math.cos(theta) + 0.0065;
      baidu_point.lat = z * Math.sin(theta) + 0.006;
      return baidu_point;
  }

  let nowMars_point = transform(+nowlat, +nowlon)
  let baidu_point = marsTobaidu(nowMars_point)
  return baidu_point
}

使用的时候直接引入

<script src="./js/transformLatLon.js"></script>

let baidu_point = transformWDS2BD(lat, lon)// lat、lon为你自己的经纬度

完结撒花，如有不妥，还请指教