Avalanche risk: preparing for an excursion with the web applications Yeti and Skitourenguru

Choosing a route suited to current snow conditions is key to reducing the risk of being caught in an avalanche. The Petzl Foundation supports Yéti and Skitourenguru, two web applications that help outdoor enthusiasts make the right choices when preparing for an outing. The aim is to reduce the number of avalanche victims in France and to encourage wider use of these tools.


Le grand Pic de la Lauzière (Savoie) par danger 2 sur Yéti (en haut) et sur Skitourenguru The Grand Pic de la Lauzière (Savoie) by danger 2 on Yeti (above) and Skitourenguru.

France holds the unenviable record of posting the highest number of avalanche deaths in the world. Over the last four decades, an average of 31 people have died in France’s mountains each year. Almost invariably, those who lose their lives are partaking in winter sports: backcountry skiing, off-piste skiing and snowshoeing. Good outing preparation is all too often neglected, but it appears to be a key factor in preventing accidents. Since December 2019, two applications that allow users to better prepare for their excursions can be accessed via the web. They allow the information available at home to be interpreted more effectively on the eve of an outing.


Yéti was developed by the National School of Geographic Sciences (ENSG), specifically Jacques Beilin and his students. The application relies on an automatic analysis of terrain characteristics, which is itself based on the digital terrain model created by the IGN (National Geographic Institute), on MétéoFrance’s avalanche bulletins and on certain risk reduction methods. Based on accidentology data, risk reduction methods are also founded on the collective knowledge gathered by hundreds of skiers, which goes far beyond what can be accumulated by a single individual, even one who is highly experienced. These methods cater for three different levels of ability and depend on the safety margin and the degree of analytical complexity the user is seeking: a risk reduction method for beginners, a basic method and a professional method.

Yéti highlights high-risk areas by overlaying colours on a map interface. A quick glance allows users to spot the riskiest slopes and identify the key sections of a route. This enables them to assess the overall safety of the route they are planning and to find backup options in lower-risk areas, if necessary. Having been successfully trialled by a panel of 80 people over the 2018/2019 winter season, Yéti will become available to the general public from December 2019 via the collaborative website The application covers all of France’s mountain ranges.

/fondation/foundation-yeti-skitourenguru-2.jpg?v=1The Grand Arc (Savoie) by danger 2 on Yeti with the elementary reduction method. The blue color shading makes it easy to identify the most dangerous slopes. was designed by Günter Schumdlach, a former student of the Zurich Federal Technical University, an IT specialist and a skier. Each day, this application automatically calculates an estimated avalanche risk for 1,100 digitised routes. The algorithm is based on the Quantitative Risk Reduction Method (QRM). The method relies on mass data processing (1,469 avalanche accidents involving people, almost 50,000 km of GPS routes and 4,656 avalanche bulletins), which provides a much sounder statistical footing than more empirical “standard” risk reduction methods. The algorithm incorporates all the information contained in avalanche bulletins and digital terrain models, including not only the incline and the direction faced, but also the proximity to ridges, tree density and the level of danger of the slopes in an area, including those overlooking the route.

The risk is calculated for every point on the route. The values for each point are then combined to produce a risk indicator for the entire route. Every day, each route is classified in one of three categories: moderate risk (green), considerable risk (orange) and high risk (red). The service, which has been available online for four years, is now recommended by every mountain institution in Switzerland, including the Swiss Alpine Club, the Institute for Snow and Avalanche Research in Davos, the Department for Youth and Sport, the Swiss Mountain Guides Association and the Swiss army. The site was initially published in German, but is now available in French, Italian and English at the following address:

A version of Skitourenguru was successfully trialled over winter 2018/2019 in the Belledonne massif between Isère and Savoie. The service will be available to French users in the Belledonne, Lauzière and Beaufortin massifs as of December 2019, before being gradually rolled out across France’s mountain ranges.

foundation-yetiThe classic route of the Grand Arc (Savoie) by danger 2 on Skitourenguru. The application allows to display the map of the slopes of the Geoportal. On that day, the avalanche bulletin indicated strong warming on the southern slopes.

To gain a deeper understanding of the Quantitative Risk Reduction Method and the Skitourenguru algorithm, you can download English language versions of Günter Schmudlach’s publications below:

Precautions when using applications to prepare for excursions.

Yéti and Skitourenguru allow more informed choices to be made by analysing as much information as is available on the eve of an outing, so as to better anticipate and assess the risks before heading out into the mountains. However, analysing the risks from the comfort of one’s home requires more than just surfing the web. Applications cannot replace the task of assessing all the risk factors covered by the 3x3 analysis table and it is particularly important to read bulletins in full.
While unlikely, avalanches can still occur in areas or on routes where the risk is low and which are not flagged as hazardous on maps created using algorithms. It is always important to assess the conditions on the ground using one’s intelligence and experience, but also by listening to one’s community, peers and companions.

The information provided by Yeti or Skitourenguru should never be the sole criteria for choosing to ski a slope.

/fondation/foundation-yeti-skitourenguru-4.jpg?v=1An avalanche of plate triggered by skiers © Olivier Moret

These two applications have the same limitations as the foundations on which they are built: avalanche bulletins, digital terrain models and risk reduction methods. Before using Yéti and Skitourenguru, it is recommended that users read the instructions carefully and inform themselves about the advantages and limitations of these applications:
- Yéti
- Skitourenguru

/fondation/foundation-yeti-skitourenguru-4.jpg?v=1Under the Pointe du Valonnet (3,371 m) in Vanoise, France © Olivier Moret

Uploaded in December 2019


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