Distances between thermals
Above flatlands, during a nice and sunny day, the Convective Boundary Layer (CBL) is turbulent. The lower part, immediately above the ground, is disturbed by wind friction on various obstacles: trees, farms and hills.
Azerables. A specific thermal?
"Azerables" is a small village in the middle of France, in "Creuse" departement. During his record flight on the 1st of May, 2016, Martin Morlet arrives close to that point at around 5 o’clock (solar time).
It is commonly accepted that thermals start from the ground. It is not always true, in particular when condensation takes place. The updraft can start directly from a lower layer, warm and wet, on top of which arrives a colder one. But under dry conditions, it is the experience of all cross country pilots.
Wind speed and direction can be measured precisely by the verticalization of circles at different points of a tracklog. The exact time of each circle is known. Then, it is easy to calculate the average wind during the flight.