地球上2点的距离

球形, 大圆距离(The Great Circle Distance)

var EARTH_RADIUS = 6378137.0;    //单位M
    var PI = Math.PI;
    
    function getRad(d){
        return d*PI/180.0;
    }
    
    /**
     * caculate the great circle distance
     * @param {Object} lat1
     * @param {Object} lng1
     * @param {Object} lat2
     * @param {Object} lng2
     */
    function getGreatCircleDistance(lat1,lng1,lat2,lng2){
        var radLat1 = getRad(lat1);
        var radLat2 = getRad(lat2);
        
        var a = radLat1 - radLat2;
        var b = getRad(lng1) - getRad(lng2);
        
        var s = 2*Math.asin(Math.sqrt(Math.pow(Math.sin(a/2),2) + Math.cos(radLat1)*Math.cos(radLat2)*Math.pow(Math.sin(b/2),2)));
        s = s*EARTH_RADIUS;
        s = Math.round(s*10000)/10000.0;
                
        return s;
    }

椭圆形 计算公式

/**
     * approx distance between two points on earth ellipsoid
     * @param {Object} lat1
     * @param {Object} lng1
     * @param {Object} lat2
     * @param {Object} lng2
     */
    function getFlatternDistance(lat1,lng1,lat2,lng2){
        var f = getRad((lat1 + lat2)/2);
        var g = getRad((lat1 - lat2)/2);
        var l = getRad((lng1 - lng2)/2);
        
        var sg = Math.sin(g);
        var sl = Math.sin(l);
        var sf = Math.sin(f);
        
        var s,c,w,r,d,h1,h2;
        var a = EARTH_RADIUS;
        var fl = 1/298.257;
        
        sg = sg*sg;
        sl = sl*sl;
        sf = sf*sf;
        
        s = sg*(1-sl) + (1-sf)*sl;
        c = (1-sg)*(1-sl) + sf*sl;
        
        w = Math.atan(Math.sqrt(s/c));
        r = Math.sqrt(s*c)/w;
        d = 2*w*a;
        h1 = (3*r -1)/2/c;
        h2 = (3*r +1)/2/s;
        
        return d*(1 + fl*(h1*sf*(1-sg) - h2*(1-sf)*sg));
    }