JAXAshby wrote:
One
could also say that the compass represents another reference


no, one can not. one can ONLY state which direction magnetic North is and
which direction relative to that the boat is pointed, but *no* deduction can be
made as to which direction actually is actually going. none.

Wrong. If someone has experience with ones particular boat, one has
experienced in the past similar conditions, so that one has an educated
feel for how much set one has under many conditions, which one can apply
to ones magnetic heading to determine which direction one is actually going.

otn