Well, it's done, for the most part.
I have now a fully functional compass, with
+ 0.5deg precision.

Taken just after out of the pen in Bergen.
As an help, I put a listing of the meridiens and parallels' scales in the map window.
If you don't mind editing your menu_1024_768.cfg, you could move the block given by Kaleun Freddie for the sextant to the G34 group (you'll need to change the ParentID for that of the group) and then, the sextant will be only available in exterior view, as it should be, IMO.
Im also thinking of having an access to the SS/SR chart in game, but I don't know if I could succed in such a try....:hmm: