为什么地图上的圆圈大小会发生变化？

Question

这是一个说明我的问题的演示：我在半径为 500000 的地图上画了一个圆，但在一个位置圆看起来更大。我试着检查了地图的缩放比例，它总是一样的。

place = {
name1:[-33.8650, 151.2094],
name2:[59.3293, 18.0686]
};

var id,circle,center;

function panMap() {
    id=this.getAttribute('id');
    center=place[id];
    map.panTo(center);
    circle = L.circle(center,500000, {
                 color: 'red',
                 fillColor: '#f03',
                 fillOpacity: 0.5
                 }).addTo(map);
    console.log("zoom = " +map.getZoom());
};

// center of the map
var center = [29,29];

// Create the map
var map = L.map('map').setView(center, 3);

// Set up the OSM layer
L.tileLayer(
  'http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
    maxZoom: 18
  }).addTo(map);
  
var classname = document.getElementsByTagName("button");
for (var i=0;i<classname.length;i++) {
    classname[i].addEventListener("click", panMap, false);  
};

.container {
  height: 30px;
  width:100%;
}
#map {
  height: 400px;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/leaflet/1.0.0-beta.2.rc.2/leaflet.js"></script>
<link rel="stylesheet" type="text/css" href="https://cdnjs.cloudflare.com/ajax/libs/leaflet/1.0.0-beta.2.rc.2/leaflet.css">

<div class="container">
<button id="name1">place1</button>
<button id="name2">place2</button>
</div>
<div id="map"></div>

Answer 1

这是由于 Mercator projection。引用维基百科：

the Mercator projection distorts the size of objects as the latitude increases from the Equator to the poles, where the scale becomes infinite

place1的纬度比place2的纬度更靠近赤道，因此显得更小。

为什么地图上的圆圈大小会发生变化？

Why does circle circle size change on map?

javascript

openstreetmap

leaflet