Is there a helper function / formula to keep the circle overlay constant while zoom in/out within Google Map?

I'm using GMap V3 API Circle to display the event location, if the more events occurs in that location, the size of the circle, i.e the radius would be bigger, in other wor开发者_StackOverflowds, the size of circle only relates to the event number occur in that location.

However, the radius of circle API is in meters on the Earth Surface, which means if I zoom in/out, the visual size of circle varies, so is there some function or formula to keep the circle size constant no matter which zoom level I'm in?

Thank you!

Ryan

I haven't seen any function to make the constant circle overlay on Google map. So the alternative solution which I am using that I have make the image of circle and then use the marker overlay with custom image on Google map. Following is the code of marker overlay.

var image = 'circle.png';
var beachMarker = new google.maps.Marker({
position: centerPoint,
map: map,
icon: image,
});