How many times have we argued for this? We always do this in hang
gliding.

http://www.naviter.com/2015/02/gps-altitude-vs-pressure-altitude/

The CIVL Plenary – the Paragliding and Hang Gliding body of the
FAI – has decided to use Pressure Altitude for scoring competition flights.

It was a difficult and a very long decision making process for the paragliding
officials to do away with the GPS altitude. GPS altitude has always been used to
verify the altitudes in paragliding competitions and it has all to do with the
roots of where paragliding is coming from. Recently however many GPS altitude
related controversies have convinced the CIVL to re-consider using pressure
altitude rather than the GPS altitude to improve reliability and accuracy of the
measurements.

Andrej Kolar from Naviter was invited to do a presentation at the CIVL Bureau
meeting in Belgrade due to the experience Naviter has with scoring sailplane
competitions world-wide. We would like to share the keynotes from the
presentation and the conversations that followed.

The pros and cons of pressure altitude versus GPS altitude:

Our varios are capable of delivering a reliable sound when climbing in 0.1
m/s. In order to do that they need to react to an amazingly small difference in
pressure produced by a column of air no taller than 8 cm (~3 inch). Imagine the
weight of 8 cm of air in a small tube!



The delegates at the CIVL bureau meeting took their time to fully understand
this. It was a long and interesting discussion. The result of it was that the
implementation of Pressure Altitude for Category 1 events was promoted from
being mandatory in 2016 to it being mandatory starting in May 2015.

It is now the standard for all aviation sports and we are very happy to have
played a small part in this rule being implemented. We congratulate the CIVL for
its openness and wisdom in getting this change approved and promoted through the
sport.

See the link for graphical comparisons.