NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Help - Unknown Compass Graduation Arrangement
From: Joe Schultz
Date: 2009 Oct 23, 00:36 -0700
From: Joe Schultz
Date: 2009 Oct 23, 00:36 -0700
Hi Frank, Sounds like unit of "mils," originally developed for US Army artillery. Officially 6400 divisions in a circle - you can do the geometry to see how that works in a metric distance system. Your compass, if with a mirror, is called a sighting compass or sometimes a transit compass. I use my $10 lensatic compass (no mirror) extensively in terrestial navigation, pretending there are 640 mils in a circle (there are 640 divisions on the compass card). I can then resolve 360/640 = 9/16 degree on the compass, and split that twice without squinting too hard through the built-in magnifier. A hand-made conversion table easily converts between degrees and mils, 5 inches square and laminated. To complete the picture, British artillery developed the "grad," or 400 divisions in a circle. If you have a trig calculator then you can probably do trigonometry in grads, degrees or radians. Joe --~--~---------~--~----~------------~-------~--~----~ NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To , email NavList+@fer3.com -~----------~----~----~----~------~----~------~--~---
