From an early age, many of us learned that the Mont Blanc’s altitude was 4807.2 meters, a measurement established by the Vallots in 1894 with impressive precision for the time. It was stopped in 1894, with a precision they estimated at the time to be in the order of half a metre. Subsequently, this altitude was incorporated into the SGA (Service Général des Armées) benchmarks and became official. It would not be questioned until the end of the 20th century… and would be memorized by generations of schoolchildren. This altitude became an official reference, unchanged for over a century.

Measuring Europe’s roof in the 21st century

It was only in 2001 that geomètres-experts decided to update this historic measurement. Organizing bi-annual surveys, the Chambre Départementale des Géomètres-Experts de la Haute-Savoie seeks not only to determine the altitude of Mont Blanc, but also to model its ice cap. This will enable us to build up and feed a bank of accurate, reliable data that can be used by experts (glaciologists, climatologists, etc.) and, above all, passed on to future generations.

This valuable data will be used by various specialists and passed on to future generations. The last measurement took place between September 14 and 16, 2023.

Details of expedition 2023

The team faced :
– A 10-hour ascent.
– 8 groups, or 22 participants, including surveyors, guides and photographers.
– An altitude difference of 2,500 metres, with 10 kg of equipment per person.
– Ideal conditions for precision measurement.
– A one-hour measurement session, using GNSS technology and over 1,300 drone images.

Mont Blanc – Source: Wikimedia Commons

Mont Blanc’s altitude is now 4805.59 metres

In 2019, a particularly low measurement was recorded. 2021 saw an increase of 1.80 meters on that measurement. What about 2023? The time has finally come to reveal the long-awaited altitude of Mont Blanc, version 2023, with an accuracy of 2 to 5 centimetres. The answer is 4805.59 metres, confirming a downward trend.

Now it’s up to climatologists, glaciologists and other scientists to exploit all the data collected and put forward all the hypotheses to explain this phenomenon.

The aim of these expeditions is also to demonstrate to new generations the essential and exciting role played by surveyors. They are the guardians of territorial data, playing a crucial role for France.

Martin Fourcade, a renowned biathlete, underlined his fascination for Mont Blanc and even joined the experts this year, attesting to the importance of this mission: “Mont Blanc fascinates me. It’s like an emblem of our heritage. I didn’t hesitate. Mountains are my element. It was a challenge”.