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<script>
window.onload=function(){
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;
}
/**
* 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));
}
console.log(getGreatCircleDistance(39.87945682,116.64095684,39.91406638,116.60629272))
console.log(getFlatternDistance(39.87945682,116.64095684,39.91406638,116.60629272))
}
</script>
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