Wandering Daisy wrote: ↑Wed Feb 06, 2019 7:09 pmI am not implying that backpackers use professional survey gear. I simply mentioned surveyors because sometimes the general public is not aware that small angle errors add up to a lot at distances. The real point is why not just KNOW what the current declination is and adjust to the current declination? Although cheaper compasses have errors of that magnitude, at least you are starting from the actual declination. Errors can be additive.
Well yes, of course you should use the current declination if you know what it is. But the concern that the relatively rapid change in the magnetic north pole position is an important factor for navigating in the Sierra is what I'm saying isn't true. If you get lost using a compass it won't be because you used the 1979 declination instead.