I totally agree about the electronic compass combined somehow with GPS. The only one (digital compass module) that I could afford as a hobbist only had 8 degree accuracy. It could be the same one that MK uses. When my MK autopilot does heading corrections, it looks to move about 8 degree increments during these correctional moves. I don't know. I am an outsider with good guessing abilities (glass ball and Ouigi board).

The down side to the compass is it doesn't take into account the physical influences such as wind, water, tidal action, moon phases, etc. There is an answer, it just ain't in my glass ball yet.