Bear in mind that "map" is not a constant. Some maps are a whole lot better than others - planimetric vs.topographic, large scale vs small scale, recent vs old ( has it been updated in the last ten years? - may or may not be vital), and most importantly, when the map was in production, did anyone carry out a competent field check. While most USGS maps are quite good, I have seen some with mislabeled features and trails placed with the help of a cold brewski in a backcountry bar..

What is interesting is that for many of us, the compass is a rarely used item - well, the better ones do have a mirror that is nice for shaving and signalling.