I think you may be missing the point in the posts above.
The plane doesn't measure the air movement or wind.
The Inertial systems measure the relative movement of the plane along a track and compare that with the commanded course, heading, and attitude the plane maintains plus the airspeed as computed inertially vs. the air data measured airspeed and then presents the difference to the pilot as a wind vector.
If you're doing 100kts CAS with a course of 90deg. and the inertial figures you're doing 50kts along a 90deg track then you have a wind of 90deg at 50kts. (and that's a bit simplified but we don't need to be getting into TAS, GS, IAS, and CAS now do we?)
Or do I have it backward again???
I'm so confused..........
