On Tuesday, 14 January 2014 04:46:19 UTC+2, Eric Greenwell wrote:
Steve Leonard wrote, On 1/13/2014 8:17 AM:

On Monday, January 13, 2014 2:34:40 AM UTC-6, krasw wrote:

Yes, theoretically *if* thermals would drift perfectly with

wind...



Uh oh. Next problem. If thermals don't drift at the same speed as

the wind, how accurate is that wind speed your computer derrives from

drift while you are thermalling?



My experience with a 302 and SeeYou Mobile was the differences were

small compared to other variations due to time, location, and altitude,

and small enough that I usually didn't notice any difference. But, there

may be places that do have bigger differences, and I just didn't fly there.



--

Eric Greenwell - Washington State, USA (change ".netto" to ".us" to

email me)

I think many computers (or software) counts for wind variations due altitude. For flying in convective conditions this is just plain wrong and misleading. Wind doesn't change much (or at all) between altitude just over surface friction layer (few hundred meters) and cloudbase. This is because convection effectively mixes airmass momentum in convective layer. (Wave and mountains are of course different matter). Most important variations are due location and time.