如何在谷歌地图500米的距离放两个标记 [英] how to put two marker at a distance of 500m in google map

问题描述

我们如何在500米的距离放置两个标记，让第一个标记的latLng为伦敦（51,0），第二个标记放置在距离该标记500m的距离处。我已经尝试过任何事情，但无法找到并回答它..任何想法

How we can put two markers at a distance of 500 meter, lets say latLng for first marker is london (51,0) and second marker is put ad a distance of 500m from this marker. I have tried ever thing but couldnt find and answer for it.. any ideas

推荐答案

我已经查看了Google Maps API和它似乎我的回答是错误的。我没有注意到latLng不适用于长度而是经度和纬度（它看起来好像我忘记了地球不平坦:)）。使用这个漂亮的网站，我能够想出更好的解决方案：

I have looked into Google Maps API and it appears that my answer was really wrong. I haven't noticed that latLng doesn't work with length but latitude and longitude (it looks as if i have forgotten that earth is not flat :) ). Using this nice web site I was able to came up with better solution:

var position = new google.maps.LatLng(51.517289, -0.130463);  
var latlngs = [];
var map;
// distance from position in km
var d = 5;
// Earth radius
var R = 6372;

function initialize()
{
    var mapOptions = { zoom: 12,
              mapTypeId: google.maps.MapTypeId.ROADMAP,
              center: position };    
    map = new google.maps.Map(document.getElementById("map_canvas"),
            mapOptions);
}

function dropMarkers()
{
    var lat1Deg = position.lat();
    var lon1Deg = position.lng();
    var lat1Rad = lat1Deg.toRad();
    var lon1Rad = lon1Deg.toRad();

    latlngs.push(new google.maps.Marker({
        position: position,
        map: map,
        draggable: false,
        animation: google.maps.Animation.DROP}));

    for (var brngDeg = 0; brngDeg < 360; brngDeg+=20)
    {
        brngRad = brngDeg.toRad();
        var lat2Rad = Math.asin( Math.sin(lat1Rad)*Math.cos(d/R) + 
                      Math.cos(lat1Rad)*Math.sin(d/R)*Math.cos(brngRad) );
        var lon2Rad = lon1Rad + 
                      Math.atan2(Math.sin(brngRad)*Math.sin(d/R)*Math.cos(lat1Rad),  
                      Math.cos(d/R)-Math.sin(lat1Rad)*Math.sin(lat2Rad));

        lat2Deg = lat2Rad.toDeg();
        lon2Deg = lon2Rad.toDeg();
        latlngs.push(new google.maps.Marker({
                    position: new google.maps.LatLng(lat2Deg,lon2Deg),
                    map: map,
                    draggable: false,
                    animation: google.maps.Animation.DROP}));
    }
}

if (typeof(Number.prototype.toRad) === "undefined")
{
    Number.prototype.toRad = function()
    {
    return this * Math.PI / 180;
    }
}
if (typeof(Number.prototype.toDeg) === "undefined")
{
    Number.prototype.toDeg = function()
    {
    return this * 180 / Math.PI;
    }
}   

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