UNIL Scientists Identify the Actual Highest Peak in the Jura

Located to the north-west of the Alps, along the border between France and Switzerland, the Jura massif stretches over 360 kilometers. The highest peaks are found in the French part. According to measurements taken since the 19th century, two peaks have been vying for the title of highest point: Crêt de la Neige and Le Reculet. Even today, not all the available topographical maps agree on their altitudes.

This curiosity caught the attention of György Hetényi, a keen hiker and orienteer who also teaches at the University of Lausanne's Institute of Earth Sciences (ISTE). “I noticed an intriguing and somewhat unclear contour line on one of the maps”, he comments.
At his instigation, a team of UNIL specialists got together and, with the authorization of the prefecture of Ain (FR), conducted a high-precision GPS measurement campaign in July. The result is clear: Crêt de la Neige is not the highest peak in the Jura. A hitherto unnamed peak further away in the same area stands 2.75 meters taller.

J1 is the highest peak in the Jura Massif
The scientists named it “J1”, in a nod to the famous K2 in Karakorum (Pakistan), which takes its name from the notation used for anonymous peaks in the first drawing in which it appeared. The final ranking is as follows: J1 now stands as the highest peak in the Jura massif, with an elevation of 1,720.83 meters. It is followed by Crêt de la Neige and another newly measured peak, J2, both reaching 1,718 meters and a few centimeters. Le Reculet comes in last at 1,717.14 meters. Measurements were taken at the highest fixed rock point on each peak and have a maximum error margin of 5 centimeters (see box). The results have been published in the Mémoires de Géologie (Lausanne).

“We were expecting a difference, but not such a significant one" says György Hetényi. "J1 likely went unnoticed until now because it’s not very prominent—it's surrounded by trees, and traditional triangulation methods rely on the visibility between peaks.
As Crêt de la Neige, J1 is located in the Haute Chaîne du Jura National Nature Reserve, an area that is home to exceptional and rare flora and fauna, including the capercaillie and the lynx. The delicate balance of this ecosystem is particularly vulnerable to human disturbance, especially off-trail activities. To safeguard the area, the exact location of J1 has not been disclosed. The experts' internal report has been submitted to the Haute Chaîne du Jura National Nature Reserve, the French Institut national de l'information géographique et forestière (IGN) and the Swiss Federal Office of Topography (swisstopo).

Calculation method
The UNIL team used a method called differential GPS. The scientists installed a professional antenna at the J1 point and left it there for 4 hours as a “base”, enabling them to obtain its location and altitude with centimeter-level accuracy, using satellites and the permanent GPS network. Another GPS antenna was brought successively to the other three points and left there for 30 minutes each time. This simultaneous operation with the base enables the mobile GPS or “rover” to achieve very precise relative positioning, and to record the necessary corrections supplied by the base. The final error margin is plus or minus 5 centimeters for the elevation of J1, and of the order of a centimeter for the relative positioning of the other peaks in relation to J1.

The measurement campaign was carried out on July 2, 2024 by a four-person team from UNIL's ISTE: György Hetényi, Anne-Marie Chagros, Kim Lemke, Ariane Maharaj; calculations were carried out by György Hetényi and Ludovic Baron.

Source: G. Hetényi, A-M. Chagros, K. Lemke, A. Maharaj, L. Baron (2024) Détermination du point culminant du massif du Jura, Mémoires de Géologie (Lausanne), n° 51, 6 pp.