谷歌地图控制圆圈随缩放自适应大小 js

var circleOptions = {
strokeColor:"#95C7F9",
strokeOpacity:1,
strokeWeight:0.5,
fillColor:"#95C7F9",
fillOpacity:0.35,
map:map.map,
center:position
};
map.locateCircle = new google.maps.Circle(circleOptions);
google.maps.event.addListener(map.map, 'zoom_changed', function() {
var p = Math.pow(2, (21 - map.getZoom()));
map.locateCircle.setRadius(p * 1128.497220 * 0.0027);
});