I use this;
http://www.subsim.com/radioroom/down...?do=file&id=89
along with this;
http://www.subsim.com/radioroom/down...p?do=file&id=9
Once you get used to using the range rings along with the range settings you'll probably never look at the A scope again.
Range knob is set for 20,000 yards, so that's the outer edge of the PPI scope. At that setting the rings are 5,000, 10,000, and 15,000 yards. The dot bearing 075 is between the 10,000 and 15,000 yard rings, not quite halfway so about 11,500 to 12,000 yards. That's actually a lot more accurate than you'll get with the spike on the A scope.