At 01:37 04 June 2020, wrote:
On Wednesday, June 3, 2020 at 8:39:12 PM UTC-4, Dave Nadler wrote:
On Wednesday, June 3, 2020 at 7:33:52 PM UTC-4, weemacgregor wrote:
Is the speed at which a thermal drifts the same as the winds aloft?

Yes
and
No... If the thermal is being produced by a power station chimney, then
20 feet higher than the chimney, the drift of the thermal is zero. It is
only when the thermal reaches a few thousand feet above the chimney that
the drift equals the wind aloft speed.

Also remember that for even higher altitudes your IAS is not your TAS, so
on a calm day, your GPS speed will differ from your IAS. ( about +2% per
1000ft.)