Mxsmanic,

So the compass cannot always be trusted.


Yes, it can. Compass turning error is well-defined - any pilot
understands it and takes it into account.

Again and again: Why can't you acknowlegde that there are things you
don't know anything about? Just shut your mouth and learn instead of
coming back with smart*ss comments over and over again.

--
Thomas Borchert (EDDH)