Off-Piste skiing before and after FATMAP

FATMAP is our favourite app for detailed off-piste / backcountry skiing data and informed decision-making.  It is only useful if you know how to read and interpret the avalanche bulletin (see here and here), can work with slope angles and exposition to minimise the risk of provoking avalanches, are familiar with avoiding terrain traps and equipped with ARVA/shovel/probe and maybe an airbag and are trained and practised in using all of the above (See here).

Life before FATMAP

You’re not invincible

Life after FATMAP

You’re still not invincible

Planning your day

“I know some great off-piste lines that not many people know about…”

“Of course I’m sure it’s safe – I’ve skied it loads of times before!”

“We always go that way”

“Here, let me take you to my favourite line.”

“Yeah! Look where those guys are going… let’s follow them!”

“I’ve always wondered where those tracks end up, shall we look and see?”

“What an amazing powder day! Shall we try that run over the back today?”

“Trust me, I know what I’m doing… You guys are good skiers too, right?”

Planning your day

Use the high-definition 3D terrain maps as you would use Google-Earth, pinch and zoom, rotate and change the aspect to fully explore the mountain contours

Examine all the famous off-piste lines that are clearly shown on the map, click on the line to pull up a data file with all the key stats you need to decide whether it is a safe enough choice for today or not

Read the description on what to expect, learn of specific hazards, understand the skill levels required, how to access it, how to get back afterwards…

Armed with the information from the avalanche bulletin, review the graphics showing slope angle, exposition, elevation and decide if the route could be an option for the day

View a “fly-through” to see what the terrain should look like while skiing it

Dropping in

“Wow that’s a lot of fresh snow… it didn’t look like this last time…”

“It’s gotta be around here somewhere…”

“I’m not sure, I just heard that we had to climb up here on the left and over a ridge and then it would open out into a big powder bowl.”

“Let’s just follow those tracks and we’re bound to get onto the right line”

“Do you think we should go left or right around those rocks?”

“If we ski down to that ridge we should be able to see where to go next”

“I don’t think it’s that way, that doesn’t seem right to me.”

“What do you think?”

Dropping in

Armed with further clues from looking and asking around and monitoring the developing weather and snow conditions on the way to the drop-in, the GPS locator ensures you are at the right starting point

If you decide at this point that the conditions are too risky, you only need to head off somewhere for a hot chocolate and choose a less-risky route

On the way down, use the islands-of-safety, pick your route to avoid the terrain traps and nearby steep slopes, look to confirm the location of other hazards that you read about

The GPS locator tracks your ride all the way to the end and stores it in the app. You know where you are at all times, which can be a very useful back-up in an unexpected white-out or a rescue situation


Reviewing the day

“We went over the back around here somewhere, hiked up and over there and finished up around about here.”

“Check-out my GoPro footage when I get around to processing it and post it online!”




Reviewing the day

Review your actual route as a “fly-through” and check out how closely you followed the recommended line, check your stats, learn from your mistakes, submit information to improve the app content

Instantly share it with your friends in the après-ski bar,

Upload it as a video, keep your own notes for future reference as a logbook based on your own experience, without risk of forgetting the details.


FATMAP in their own words 

Welcome to FATMAP 

 Welcome to FATMAP – a new mapping technology for outdoor environments – a map, guide book, terrain toolkit and local insider all in one. We created FATMAP when we realised that current ski maps – on or off the piste – don’t give people the information they really need to know to make the most of their skiing.

 At FATMAP’s core is an ultra-high resolution 3d model of the terrain to which we have added the essential information you want as a skier. 

 Whole ski areas have been mapped together with descriptions and detailed information to help you make better decisions about where to ski. Want to know where to find the moguls, which runs will be in the sun or where to find the steepest black runs? Looking for a restaurant with a nice sunny terrace for lunch? It’s all here in FATMAP. 

 Check out user comments and ratings for every line and use 3D fly-throughs to help you see and experience your chosen line virtually before you set out. Locate yourself with precision on the map and share your location with your friends so you never get separated again. And record your performance to keep track of your stats throughout the day. 

 For people wanting to venture off-piste, FATMAP gives you detailed information about the lines plus a whole terrain intelligence toolkit to understand gradient, aspect, altitude, avalanche and crevasse zones. 

 It is important to note that FATMAP is designed as a tool that provides you with information to make your own decisions. We are not suggesting or encouraging you to cross the safety barriers of the ski resort. Off-piste skiing is a dangerous sport which requires a great deal of expertise. There is no such thing as zero risk. 

FATMAP will never replace the knowledge and experience of a professional. You always ski at your own risk. FATMAP is the manifestation of a lifelong-obsession with maps, a mis-spent youth with computers, a friendship founded in the mountains, and a shared ski addiction. We’ve worked with pro skiers, Mountain Guides, Mountain Rescue Associations and skiers everywhere to create FATMAP. We hope you like it and that it will help you to explore further and push your limits, safely. 

 Technical Details 

 FATMAP uses two different 3d models and a texture map. 

 Terrain Model – DTM 

 The base data for FATMAP is an ultra-high resolution 3d model of the terrain. Our model has the average height of every 2m2 area of terrain. The terrain model (DTM) shows the ground surface. It does not account for trees, rocks or buildings. It provides an accurate representation of the terrain to calculate gradient and other information. Our terrain models are created using aerial and satellite imagery. Whilst extremely accurate they have an error margin of +/- 3m. Surface Model – DSM In addition to the DTM we have a surface model which provides information about the surface of the terrain – including trees, buildings, large rocks and other objects. This provides a true-to-life view of the world as we see it. In Swiss areas we only have a surface model up to an altitude of 2000m so trees and other objects above this altitude do not appear in 3d on the model.

Texture Map

To bring FATMAP to life and show the terrain as it is in real-life, our terrain model is overlaid with the latest winter satellite imagery. Different areas use different satellites based on availability. Imagery is either 40cm monochrome or 50cm colour imagery which means each pixel of the image covers an area of 40cm or 50cm on the ground. The imagery has been ortho-rectified to the terrain model (DTM) so that it provides excellent GPS positional accuracy. The imagery is not live but provides a useful indication of the typical snow cover during the winter. You will need to inform yourself about the actual snow cover in the resort before setting out. 


 As one of the largest ski areas in Europe, Verbier exists as both a top-class ski resort and cosmopolitan get-away. This combination has drawn many a skier and snowboarder, regardless of their experience level, as well as those looking for a relaxing holiday and lively nightlife. Its location on a sunny plateau at the heart of the 4 valleys grants easy accessibility to those coming from Britain, Netherlands and the Scandinavian regions, giving the area a vibrant and diverse culture. It’s known as a premiere off-piste ski area with infamous runs like the Back-Side of Mont Fort, Stairway to Heaven and the Couloir de la Banane. Perhaps the most intimidating run is the Bec des Rosses. This run hosts the annual Freeride World Tour which ends its exhibition of the world’s most adventurous athletes on Verbier’s excellent slopes. This massive area joining Nendaz, Veysonnaz, La Tzoumazand and Val de Bagnes all create the 4 Vallées. With 94 lifts and over 400km of piste, all which can be serviced by one lift pass, offers endless opportunity of exploration. From the resort at 1500m, heights of more than 2700m can be reached by two consecutive gondola rides that take under 11 minutes in total. There, the high altitude guarantees abundant snow. A regular, free shuttle bus links the Médran gondola with the lifts for the other, smaller ski areas via different routes among the chalets – it also provides the majority of people with access to the central area and its slopes.

Off Piste Skiing

Off-piste skiing outside the safety of the marked pistes carries with it significant risks. There are many routes detailed in each area, of varying seriousness and technical difficulty. There are routes just by the side of the piste, others far away from the resort in alpine terrain including glaciers and everything in between. Each route will necessitate a different approach. One which is solely your responsibility. Whether it is avalanches, crevasses, cliffs, steep terrain, navigation or other hazards, know that the dangers involved in off-piste skiing can kill you. It is important to note that FATMAP is not something that will make decisions for you. It will not tell you where and when to go, where is and isn’t safe, guarantee outcomes or your safety in any way. It is not the only tool you will need and it definitely does not replace your eyes, ears or brain. 

  •  Know the conditions and weather forecast – and keep track of them throughout the day Read the avalanche bulletin carefully Learn about avalanche safety – take a course. 
  •  Have the right equipment and know how to use it (e.g. transceiver, shovel and probe). 
  •  Never follow tracks blindly Ski according to your ability
  •  Tell people where you are going and what you are planning Always ski in a group and never venture off on your own Always be prepared to turn back 
  •  Avoid the steepest sections of a given slope 
  •  Always travel with a good distance between you and descend key passages one at a time
  •  Ski within visibility of each other. 
  • Stop and regroup on islands of safety. 
  •  Ski in small groups of similar ability 
  •  More experienced skiers should be both at the front and at the back 
  •  Avoid steep slopes at the sides of gullies, slopes with roll overs and slopes where wind-slabs form. 
  •  Avoid long traverses – or if one cannot be avoided, stay as high as possible. 

 FATMAP also includes some marked itinerary runs. These are runs which are marked and avalanche controlled by the ski resort. They are still considered off-piste runs which are not maintained or controlled. Whilst avalanche controlled, all the other dangers of off-piste skiing exist and they should not be underestimated. If you don’t feel that you have sufficient expertise, or don’t feel comfortable with taking on the full responsibility of decision making off-piste, we strongly recommend hiring a UIAGM/IFMGA mountain guide. 


Some of the terrain in FATMAP is glaciated. This terrain can be identified using the Crevasse Zone feature available with a FREERIDE subscription. Skiing on glaciers carries additional risk and demands a level high level of experience and skill. Crevasses are the principle danger when skiing on a glacier. In the winter, crevasses are often covered by snow bridges that can give way under the weight of a single skier. Glaciers are moving all the time and it is not possible to ‘map’ crevasses accurately on a map. Whilst different ‘risk zones’ are defined in FATMAP, you ski at your own risk and with the understanding that crevasses may form anywhere on a glacier. Crevasses are a serious danger that carry the risk of death.

  • Find out about conditions on a glacier before setting out
  •  Ski in a controlled manner
  •  Always wear a harness and carry safety equipment (rope, pulley system / crevasse rescue kit etc.) when skiing on a glacier
  • Never take your skis or board off Cross snow bridges with some momentum – don’t stop in the middle 
  • Rope up if necessary 


 Essential equipment for off-piste skiing 

 Avalanche transceiver

 An essential item for off-piste skiing. You should wear a transceiver whenever you ski off-piste. The device transmits a signal/digital beacon which allows a buried person to be found using another transceiver. It is essential to practice using a transceiver regularly. Statistics show that there is 95% chance of finding a victim alive if they are found and dug out of the snow within 15 minutes. Make sure you check all the transceivers in your group are switched on and working. 

 Avalanche probe 

 Essential to locate a buried person precisely during the final stages of a transceiver search. Carry a sturdy probe and know how to use it.

 Snow shovel 

 The last of the absolutely essential three items. You need a shovel to dig for a buried friend. Carry a shovel with a metal blade and a long, sturdy (preferably extensible) handle. Learn shovelling techniques and practice – it’s not as straightforward as it might sound! 


 Recent research and statistics show that airbags increase your chances of survival in an avalanche and are quickly becoming standard avalanche safety equipment for many people. Map & Compass & Altimeter

 FATMAP is an excellent tool, but it only works so long as your battery lasts. We strongly recommend you always carry an altimeter, compass and contour map which also has additional information not shown in FATMAP.


 For attracting attention in case of an accident. 

 First aid kit 

 Carry an emergency blanket, spare sunglasses/goggles, basic medicines, bandages, plasters and compresses as a minimum. 

 Decision Making 3×3

 Decision-making involves examining, choosing, and carrying out options. When off-piste skiing the decisions we need to make can be complex. There is a lot to think about at once and using a framework can be useful as a reminder and to ensure you don’t forget something and think about things systematically. The ‘3 × 3 Filter’ developed by Werner Munter is a commonly used probabilistic strategy of decision-making in the mountains, particularly for the assessment of avalanche risk. 

Three avalanche factors are looked at through three regional filters. The aim of the 3×3 filter method is to minimize the risk of triggering an avalanche as much as possible. In practice, this means to work out whether we believe a certain slope is safe to travel on. 

Three key avalanche factors to consider are:

  • Conditions (snow and weather)
  •  Avalanche terrain (principally gradient)
  •  People (person moving in the terrain) 

These can be considered from three different perspectives:

  • Regional
  • Local
  • Zonal (individual slope)

Always start with an assessm Regional Local Zonal (individual slope) ent of avalanche risk at a regional level. Check the avalanche bulletin reports and weather forecasts and understand the conditions and general danger levels in the region. 

 Once in a local area, constantly observe your surroundings to help identify possible danger zones – and perhaps differences with your earlier assessment at a regional level. 

 When evaluating individual slopes for a decent, look at the terrain for clues of potential avalanche danger. 

 The general concept is that when you look at the three key avalanche factors for each of the three perspectives and therefore 9 times come to the conclusion that conditions are good/safe, it is reasonable to continue. If, however one or more times we come to the conclusion that conditions are not right then we can adjust our plan and do not ski to avoid putting our lives at risk. Always start with a regional assessment (preparation), followed by the local evaluation (area assessment) and finally look at the individual slope. 

 Avalanche Risk 

 Source: ANENA, France People die in avalanches every year. The chance of being killed in an avalanche is estimated at about 15% once you are in an avalanche and the chance of survival once buried diminishes very quickly from almost 95% in the first 15 minutes (unless the avalanche has caused fatal injury) to 35% after 35 mins. When skiing off-piste, everyone in your group should carry an avalanche transceiver, shovel and probe. A shovel or probe between two is NOT sufficient. The absence of any one piece of equipment undermines the usefulness of the others and compromises your safety. Regular training is essential and it is important to recognise that this equipment is a last resort should the worst happen. It is much better to avoid avalanches in the first place. 

 Key Factors

 There are a number of key factors involved in assessing avalanche danger. 

The main ones are:


 The risk of avalanches increases with the angle of the slope. Beyond 30 degrees, all slopes can potentially be unstable – although rare, avalanches are possible below this gradient, particularly wet snow avalanches in spring time. It is possible to trigger an avalanche remotely – potentially setting off slopes that are above you when you are on a flat – from as far away as 150m. Even very gentle slopes can be threatened by avalanches coming from above and lower slopes can be threatened by avalanches coming from the slope opposite. Avalanche risk is also affected by the nature of the terrain surface, profile, aspect and wind. 

 Fresh snow 

 New snow affects avalanche risk significantly. 10-20cm of new snow in unfavourable conditions is enough to increase the risk to CONSIDERABLE. 

 Snow Pack 

 The structure of the snow pack is a key factor affecting avalanches. Fragile layers in the snow pack can create layers on which others can slide. Weighting of the snow pack, by a skier for example, can cause a fragile layer to break, triggering a slide. Wind The wind transports snow and deposits it on lee slopes forming a ‘slab’’. This is the principle mechanism by which windslab avalanches form which are particularly dangerous for skiers. A warm wind can also increase the avalanche risk, particularly if it continues for some time. 


 For cold and dry snow. In low temperatures, below 0 degrees, the increased risk of avalanche can persist for several days after a snow fall. A rise in temperature above 0 degrees increases the avalanche risk in the short term, but also causes the snow to stabilise. The first time the zero degree isotherm rises above 3000m in the season is one of the three typical avalanche situations. In spring time slopes which are stable in the morning can become dangerous due to the warm temperatures which can cause wet snow avalanches.

 Munter Elementary Reduction Method 

 The Elementary Reduction Method is a method developed by Werner Munter from avalanche statistics in Switzerland to determine whether it is reasonable to travel on a given slope. It is an easy way for a skier or boarder to make decisions about travel in the back country without having to be an expert. In the Elementary Reduction Method a skier or boarder simply completely avoids travelling on certain slopes depending on the avalanche forecast: moderate danger level (2): avoid slopes steeper than 40° – extreme caution on 35-40 considerable danger level (3): avoid slopes steeper than 35° – extreme caution on 30-35 high danger level (4): avoid slopes steeper than 30° – extreme caution on 25-30. extreme danger level (5): avoid all off-piste. Using this method does NOT eliminate risk but the large majority of historical avalanche fatalities would have been avoided using this method. The principal avalanche problem this method addresses is slab avalanches which is the main problem that off-piste skiers and snowboarders have to deal with in the Alps. It is possible for wet snow avalanches to occur on gradients lower than this but these are principally a problem in late winter and spring only, often easier to predict and typically play a smaller role in skier/boarder avalanche fatalities. The chart below shows the recommendations of the Elementary Reduction Method. 

Reduction Method

 The FATMAP avalanche zones tool provides information about gradient to contribute to your assessment of a given slope. We highlight areas of terrain in three different bands to correspond to the Elementary Reduction Method. 

  •  30° to 35°
  •  35° to 40° 
  • Over 40° 

 These zones do not provide any indication about whether a given area is dangerous or safe. The zones can be useful in making an assessment of terrain where avalanches typically start. This should not be confused with where they can be triggered or where they can reach. It is possible to remote trigger avalanches and often reach terrain that is less steep than 30 degrees – always be aware of terrain above you and terrain traps such as gullies and depressions. 

 Using our routes 

 Each line in FATMAP is accompanied by useful information. Pistes are categorised according to their difficulty by colour (Green through to Black). These are defined by the ski resorts themselves and we have made efforts to try and ensure our map matches the latest piste map. You should never follow a closed piste it may be dangerous for yourself or others in the ski resort – e.g. avalanche risk threatening another slope or area. You should consult the resort status feature in the app and information provided by the resort themselves to understand what is open in the resort.

 Route lines

 The route lines in FATMAP have been mapped to a very high degree of accuracy. It is important to note that they show a general line and are there as a guide, not to be followed blindly. Pistes are subject to be changed by the resort at any time and whilst every endeavour has been made to ensure lines are accurate, it is possible that there exist inaccuracies in the drawn pistes. Freeride lines show the general direction and route taken by a given line. It is not a precise line to be followed. You will need to make your own route choices when in the terrain. Changes in snow conditions and other factors may change the route that a given line takes. Each route is described to provide an overview of the Piste or line and the route it takes. We have made every effort to ensure they are accurate but you should not follow the lines blindly. In addition to the description additional information is sometimes provided including: 


 The difficulty provides an indication of the technical difficulty of the skiing. It does not indicate the skill level of any approach. We provide a general indication of the difficulty in good conditions but that you should appreciate that even a MODERATE route can become quite serious in bad conditions. We have used the same grading scale used in the well-known VAMOS guides for familiarity. 

 EASY (Wide gentle slopes) 

MODERATE (slopes a little steeper of up to 25/25 degrees)

 DIFFICULT (Serious gradient of 30/35 where a real risk of slipping exists) 

V.DIFFICULT (steep skiing – 40/45 requiring extremely good technique – the risk of falling has serious consequences) 

EXTREME (extreme skiing terrain above 45 degrees – reserved for experts and professionals) 


 Each FREERIDE line has an indication of the seriousness. This should NOT be confused with an indication of the difficulty. The seriousness provides an indication of the proximity to the resort. We have used the same grading scale used in the well-known VAMOS guides for familiarity. 

 NOT SERIOUS (close to the pistes) 

QUITE SERIOUS (away from the pistes but visible from them and finishing on the piste) 

SERIOUS (little chance of being seen in case of an accident) 

VERY SERIOUS (isolated in the high mountains, skiers must be completely autonomous in every situation) 

Ski Grade – Toponeige technical skiing grade 

 Some routes include a Toponeige technical ski grade to help provide an indication of the difficulty of the route. The grade is given for the overall route, considering the length and configuration of the difficulties, rather than the hardest section only. The grade includes 5 levels. The first four have three subdivisions (for example x.1, x.2, x.3) and the fifth level is open-ended. 

 Ski 1. Initiation. Slopes do not exceed 30° with no narrow sections. Vertical descent is less than 800m. 

Ski 2. Few technical difficulties. Slopes do no exceed 35°. 

Ski 3. Some technical sections. Long slopes at 35° with very short sections at 40-45°. 

Ski 4. Couloir or steep skiing : slopes between 40 and 45° over more than 200m vertical. 

Ski 5. Starts with slopes of 45°-50° during more than 300m vertical or above 50° for more than 100m vertical. 

Ski Grade Labande

 Some routes include an indication of their difficulty using the Labande grading scale. This grade gives additional information to that provided by the Toponeige or general grade. It evaluates the difficulty of the most difficult section of downhill skiing on the route. It is essentially related to the slope but also takes into account exposure. It is split into the following grades: 

 S1: Easy descent which does not require any particular technical abilities such as forest tracks for example. 

S2: Wide slopes which are easy to manoeuvre, maybe fairly steep (25°). 

S3: Slopes up to 35° (equivalent to the steepest runs in ski resorts, on hard snow). Requires good skiing abilities in all snow conditions. 

S4: Slopes up to 45°, if exposure is low (between 30 and 40° if it is high or the passage is narrow). Very good skiing abilities are required. 

S5: Slopes between 45 and 50° or more if exposure remains low. From 40° upwards if exposure is high. As well as a perfect downhill skiing technique, control of nerves becomes very important at this level of difficulty. 

S6: Above 50° if exposure is high (which is often the case) or short stretches above 55° with little exposure. 

S7: Stretches at 60° or more, high rock bands to jump or more generally very steep or exposed terrain. 

Ski Exposure Grade

 Some of the routes shown include an exposure grade. It is intended as a general guide but should not be relied upon. The exposure grade does not take into account objective hazards (stone fall, seracs…) but only the consequences of a skier falling. 

 Exposure 1 (E1): Exposure is limited to that of the slope itself. Getting hurt is still likely if the slope is steep and/or the snow is hard.

 Exposure 2 (E2): As well as the slope itself, there are some obstacles (such as rock outcrops) which could aggravate injury.

 Exposure 3 (E3): In case of a fall, death is highly likely. Exposure 4 (E4): In case of a fall, the skier faces certain death.