File:Plotting Board Analog.jpg

Summary
Image is from "Fire Control and Position Finding: Background", Bolling W. Smith, in "American Seacoast Defenses: A Reference Guide," Mark A. Berhow, Ed., CDSG Press, McLean, VA, 2004. It comes originally from "FM 4-15: Coast Artillery Field Manual, Seacoast Artillery Fire Control and Position Finding, War Department, U.S. Government Printing Office, Washington, 1940, p. 14.