On Wednesday, March 14, 2012 12:15:16 AM UTC-7, Jim Wallis wrote:
I think Ramy is correct in this. In his calculation he is basically
assuming that he is flying his true heading - that is, he has adjusted his
true course to compensate for wind. Because of this, all of the vectors
become co-linear.

- Jim




Ramy

To clarify more, my formula is not Wind =3D TAS-GS, it is HW component
=3D
=
TAS-GS. This is the true head wind component as I explained. XCSoar does
no=
t currently show the true head wind based on TAS-GS, instead it is
calculat=
ing it from the vector head wind which is not as accurate.=20

Ramy


Precisely Jim. The formula is based on the glider track relative to the ground. Subtracting GS from TAS (assuming your flight computer provides both) will always give you a precise instantaneous head wind/ Tail wind component in the direction you heading (not the direction your nose is pointing) which is really what matters to your glide performance over the ground, and to your ground speed. The formulas that other mentioned is only relevant if you wanted to calculate the head wind in the direction your nose is pointing, but there is no real value in it.

Ramy