In article ,
Mxsmanic wrote:

But here again, I need an accurate ground speed to make these kinds of
calculations, which is problematic if I don't have an accurate position.

A possibility might be accurate knowledge of winds aloft, but how accurate is
this information going to be?

Accurate enough that this is how real pilots actually do this stuff out
in the real world. A difference of a few knots or a few degrees is not
going to wreck your navigation plan anyway.

--
Mike Ash
Radio Free Earth
Broadcasting from our climate-controlled studios deep inside the Moon