I live in Maryland where Magnetic North is about 10 degrees west of True North. Books on orienteering talk about converting True North on the map to magnetic north in the field, and vice versa, but my question is: why bother? Why not just forget about True North and when you orient your map, you orient it to Magnetic North and calculate your vector from that?( All my maps have two vectors printed on them, Magnetic North and True North)
So I orient my map to magnetic north, find out that my destination is at 240 degrees from magnetic north, and just use that figure in the field. What is the point of converting back and forth, instead of just doing everything in relation to Magnetic North?