Draw ring (not circle) in Google Maps API

Question

I would like to draw a ring 20km thick with empty 5km circle inside. I dont how how to do it. I believe it is possible.

One simple solution could be to substract one

Answer 1

Here's a slightly modified version of geocodezip's answer using the geometry library:

function getCirclePoints(center, radius, numPoints, clockwise) {
    var points = [];
    for (var i = 0; i < numPoints; ++i) {
        var angle = i * 360 / numPoints;
        if (!clockwise) {
            angle = 360 - angle;
        }

        // the maps API provides geometrical computations
        // just make sure you load the required library (libraries=geometry)
        var p = google.maps.geometry.spherical.computeOffset(center, radius, angle);
        points.push(p);
    }

    // 'close' the polygon
    points.push(points[0]);
    return points;
}

You can use it like this:

new google.maps.Polygon({
    paths: [
        getCirclePoints(yourCenter, outerRadius, numPoints, true),
        getCirclePoints(yourCenter, innerRadius, numPoints, false)
    ],
    /* other polygon options */
 });

Edit:

The geometry API can be added in Node like this (thanks to Gil Epshtain):

require('google-maps-api')(GOOGLE_API_KEY, ['geometry'])

By the time I was writing this, I used plain old JavaScript inclusion in HTML: