XC Analytics

Updrafts roots

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.

The team’s foreword

The series continues with this second post of Alain, which is also the logical continuation of the first. Here, he no longer studies a few circles, but thermal climbing as a whole, based on flights made during famous days. We learn more about the specificities of the wind, and the importance of the chosen method to understand the phenomena of the air mass.

The team’s foreword

With the XC Analytics team, we would like to offer a tribune to pilots, researchers, instructors, and all the specialists in Free Flight and Sailplane’s community, to bring their insights and expertise and on topics that fascinate them, and we hope, will fascinate you too. To start this series of the XC Lab, Alain Arnaud, retired engineer and paraglider pilot, will reveal his methodology for tracklog’s analysis, and the lessons he learns from it.
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