code: protected double getWorldRadius() {
  		if (center != null) {
  			Coordinate screenEndPoint = new Coordinate(center.getX() + radius, center.getY());
  			Coordinate worldEndPoint = mapWidget.getMapModel().getMapView().getWorldViewTransformer().viewToWorld(
  					screenEndPoint);
  			double deltaX = worldEndPoint.getX() - getWorldCenter().getX();
  			double deltaY = worldEndPoint.getY() - getWorldCenter().getY();
  			return (float) Math.sqrt((deltaX * deltaX) + (deltaY * deltaY));
  		}
  		return 0;
  	}
docs: Return the circle's radius in world length units.