[cbhl]

The problem is that the compass won't be off by just 10 degrees -- it could be off by 90 or more degrees because of overhead wires or the magnet in your wallet or anything else nearby that happens to have electricity flowing through it.

[dllthomas]

Oh, for sure there are degrees of wrong that would break any reliance on the compass - no question. My point was simply that this approach may have better results sooner.