public void remove(Element element) {
        elements.remove(element);
        fireElementRemoved(element);
        if (element instanceof Obstacle) {
            obstacles.remove(element);
            fireObstacleRemoved((Obstacle) element);
        }
        if (element instanceof AccessPoint) {
            aps.remove(element);
            fireAccessPointRemoved((AccessPoint) element);
        }
    }