GoogleMapで地図上でxxxメートルの距離をピクセル数に変換

地図上で円などを描画するときに使えるかなっと思うので

MapView mapView= (MapView)findViewById(R.id.mapId);   
Projection projection = mapView.getProjection();

GeoPoint point = new GeoPoint(lat,long);

float distance = 5000;    //例:5000m

double radian = Math.cos(Math.toRadians(point.getLatitudeE6() / 1E6));
float pixel = projection.metersToEquatorPixels(Math.round(distance/ radian));