Submitted by Eric Daniel
For those of you who were ever on the M60 series of tank, one of the nifty features it had was a built in compass. While this might not seem like a big deal, it did offer you the ability to navigate on the fly (with a conventional compass you'd have to stop the tank, dismount, get away from all the metal, and shoot an azimuth, not exactly the most streamlined of processes.)
This feature, regrettably, was omitted from the M1 series, as well as not appearing on humvees (funny thing that, not giving scouts a built-in compass.) Our solution to this dilemma was to install a "boat" style compass behind the GPS doghouse (right next to the weather station.) The compass wasn't fancy, it only ran us about $25, but it was illuminated, fluid stabilized, and weatherproof.
The neat thing about boat compasses is they can be tuned. Watercraft generate their own magnetic fields, which needs to be compensated for, not to mention the variations in the local magnetic field, and so by using one of these compasses we were able to zero out the magnetic influence of the tank, as well as compensate for the local variations. The large viewing area of compass made it easy to read through the FUP (Forward Unity Periscope) and the fluid dampening prevented the compass ball from flailing about uncontrollably as we went cross country.
That was 15+ years ago. I know there are all sorts of high speed navigation systems out there both military (Blue Force Tracker et. al.) and civilian (I own a GPS now) but I still like to carry a compass as a backup (the Earth has never let me down.) Boat compasses, also have evolved greatly. The top end ones now include GPS as well as other navigational features, but the base line model still does the trick for me. The Ritchie D-55 Explorer, for example, is fluid stabilized, internally illuminated (the night light is low visibility green) and can be configured for either 12 or 24 volt operation (you can wire it into your dome light controls.) It's got internal dampers and field compensation controls for stability and accuracy, and a detachable base so you can remove it for storage (since the base is flat you can Velcro the unit to the top of the turret, the dash, where ever.)