NavList:

I was wondering if anyone has insight into the accuracy of typical backpacking magnetic compasses.   By these I mean the hand-held variety.  

In working with students (and myself), we got a fairly large number of non-intersecting triangulation fixes when we went to three bearings.   In this case we assumed +/- 5 degrees of accuracy, but I think that the actual uncertainties are larger than that.  The most difficult part is the physical size of the compasses and the difficulty in lining it up in the direction of a target.   If I work with something like +/- 10 degrees, I feel a bit more comfortable in my estimates, but that begins to sound like a ghastly large uncertainty.   Perhaps somewhere between 5 and 10 degrees?

Obviously this isn't the arc-minute precision one hopes for with well-built sextants, but for a person who brings along one of these compasses on a backpacking trip, it's helpful to know the uncertainty.