code: @Override
  	@Pure
  	public double getDistance(Point2D<?, ?> point) {
  		double dist = super.getDistance(point);
  		dist -= this.radius;
  		return dist;
  	}
docs: Replies the distance between this MapCircle and
  point.
  
  @param point the point to compute the distance to.
  @return the distance. Should be negative if the point is inside the circle.