les dénivelés sont une "distance parcourus"
pas tout à fait... tu peux avoir 2000m de dénivelé (différence entre l'altitude et le point de départ) mais avoir parcouru bien plus si ça n'arrête pas de monter et de descendre ; je fais aussi du vélo et j'en sais quelque chose 😏
Signalons que la relation entre la pression atmosphérique et l'altitude varie en fonction de la latitude, de la saison, des conditions météorologiques et de la température. En effet, à altitude égale, la pression est plus basse en hiver, par mauvais temps, et si on s'éloigne de l'équateur. Le manque d'oxygène n'est pas le seul stress lié à l'altitude. Signalons les températures extrêmes, la sécheresse et les radiations solaires qui constituent d'autres dangers pour la santé.
C'est crédible une thèse de médecine suisse, non ?
... tout ce qu'affirme cette thèse de médecine suisse n'est vrai que si la boussole servant aux mesures est bien règlée sur l'heure d'été pendant la période estivale, et sur l'heure d'hiver dans l'autre cas ...
merci à tous pour vos contributions respectives que j'ai lues avec beaucoup d'intérêt, même si on n'a rien de vraiment "officiel", les différents éclairages permettent quand même de se faire une idée un peu plus précise, to be continued... donc 🙂
Or il se trouve que contrairement aux modèles simples appris à l’école, la couche d’atmosphère est d’épaisseur variable (je crois que ça s’explique par la rotation de la terre et donc la force centrifuge) :épaisse à l’équateur, fine au pole. Donc, si l’atmosphère est plus fine aux poles qu’à l’équateur, cela veut dire que pour une même altitude, la pression est différente aux pôles (plus faible, car la colonne d’air est plus petite) et à l’équateur (plus forte, car la colonne d’air est plus haute). D’où cette histoire que l’air est « plus dense » à l’équateur, et donc l’effet de l’altitude moindre …
Très intéressante cette discussion !
Je serai incapable d'affirmer ou d'infirmer quoique ce soit, mais j'ai également déjà entendu parler (et constaté) que les effets de l'altitude ne sont pas forcément identiques selon l'endroit où l'on se trouve sur notre petite planète... donc la latitude aurait une influence ?
Est-ce que les conditions météos (donc les variations de pression) ne jouent pas également (outre la latitude) dans ce "ressenti" de l'effet de l'altitude ?
Tu as raison malalux, il nous faudrait un vrai physicien, on nage dans le flou 🙂😏😏
Relative ou absolue, on peut adapter ces termes à l'atitudes. Je les lu plus haut, sa depent du pont de reference théoriquement l'absolue pour l'atitude c'est le niveau des oceans qui est le meme partout, c'est pour sa qu'on la choisi, mais on peu aussi donner une altitude par rapport au sol, c'est bien se que l'on fait pour les grattes ciels..
Ou alors peu etre c'est de la pression qu'il était question est donc là oui, on parle de pression relative et absolue, la difference entre les 2 est 1 bar ou 5, 10puissance5 pascal (juste 2 unité diff), se qui equivaut à la pression atmospherique au niveau de la mer.
Pas évident de trouver des infos précises et sérieuses sur le sujet sur le net. Il y a plein de sources d'infos qui confirment que la pression a une altitude donnée varie selon la latitude sans expliquer pourquoi. Mais j'ai trouvé hier une page qui semble confirmer ce qui dit Makalux : la couche atmosphérique est plus epaisse en se rapprochant de l'equateur (dû à la force centrifuge venant de la rotation de la terre), la colonne d'air est donc plus haute et donc plus "lourde" --> plus de pression. (perso j'étais à la rue avec mon histoire de croute terrestre plus epaisse...)
Ce phénomène est mêlé à d'autres paramètres comme la température, les phénomènes météo (anticyclone/dépression) et l'humidité de l'air (densité et donc poids des molécules d'eau)....à l'arrivée, il serait impossible de créer une sorte de règle de trois (permettant de dire tel sommet à telle latitude équivaut à tel sommet à telle autre latitude) qui aurait vraiment un sens.
Par contre je comprends toujours pas cette histoire d'altitude relative et absolue. L'altitude est prise par rapport au niveau de la mer, je vois pas d'ou viendrait une différence entre relatif ou absolu, une "altitude par rapport au sol" s'appelle une hauteur, mais je joue peut être sur les mots.... La seule nuance que je connaisse est dans le milieu aéronautique : les altimètres sont en fait des baromètres, ils sont calés sur une pression référence (appelé QNH pour celle au niveau de la mer et QFE pour celle au niveau du sol). Ils indiquent la hauteur par rapport à cette pression de référence selon la formule (Pression référence - Pression mesurée) * 27 (une différence de 1hPa correspond, en gros, car ce n'est pas linéaire, à 27 pieds). Mais, le QNH n'étant pas toujours le même (par exemple si il y a un anticyclone là d'ou l'on part et une depression là ou l'on va, le QNH pris au départ n'aura rapidement plus aucun sens), passé une certaine altitude, les pilotes règlent leur altimètre sur un QNH standard et fixe : 1013 hPa (pression au niveau de la mer de l'atmosphère standard). On parle donc d'altitude "QNH" et d'altitude "calage 1013".
Juste une petite correction à titre culturelle puisqu'on y est : Le niveau de la mer n'est pas le même partout 😎 Il y a des variations de l'ordre de plusieurs mètres liés à l'attraction de la lune (si je me souviens bien de mes cours d'astrphysique)
"la fabrication d'un globule rouge demande effectivement 7 à 10 par contre bonne nouvelle sa durée de vie est de 120 jours (3 mois)"
Plus précisément, la durée de vie des globules rouges varie d'une cellule à l'autre. Avec une survie de 120 jours (4 mois 😉), on s'approche du maximum, à partir de 90j (3 mois), certains GR ont un grand coup de fatigue, leur équipement enzymatique s'épuise et les GR rendent l'âme. Je parle de survie, car lorsqu'ils ils sont mis en circulation dans la masse sanguine, ces cellules très spécialisées ont perdu leur noyau.
"Par contre je comprends toujours pas cette histoire d'altitude relative et absolue."
L'altitude absolue indique une altitude déterminée par rapport au niveau de la mer, après qq ajustements. Ex: sommet de 4000m
L'altitude relative n'utilise pas le niveau de la mer comme référence, mais un autre point quelconque. Ainsi lorsque tu consultes une carte topographique l'altitude entre 2 courbes de niveau peut être de 100m, ce qui indique une altitude relative entre 2 points.
Lors de datations ont fait la même distinction. Ainsi la chronologie absolue (datation à l'aide d'isotopes) indique l'âge d'un tableau ou d'un crâne humain, alors que la chronologie relative les situera par rapport à un ou plusieurs événements sans donner un âge précis, mais indiquera si l'objet examiné est antérieur ou postérieur à un événement donné.
"Le taux d'oxygène dans l'air est toujours le même, 21% quelque soit l'altitude, c'est la pression atmosphérique qui diminue."
Pour un même volume d'air, le taux de dioxygène est variable, il n'est pas de 21%, ce pourcentage ne prenant pas en compte l'eau sous forme gazeuse, dont la concentration peut voisiner les 7%. L'eau est tj présente dans l'air même dans les déserts les plus extrêmes, ce qui explique la formation de brumes nocturnes.
Plus la température baisse, moins l'air peut contenir de l'eau à l'état gazeux. Arrivée au point de saturation (point de rosée) l'eau redevient liquide, il se forme alors des gouttelettes (brouillard, nuages, brume expiratoire).
Following your recommendations, I’m starting this thread because I’m planning to do the Central Circuit in 5 days in the Rwenzori Mountains, aiming to reach Margherita Peak.
I’ve been in touch with Rwenzori Mountaineering Services, who’ve offered me a deal for $1300 with 2 guides, 1 cook, and 3 porters.
A bank transfer is required upfront.
I’d love to hear from anyone who’s done this trek or others in these mountains.
Hi everyone, we’re traveling by bike, but the same question comes up for hiking: what simple products can we find in towns or villages to eat/cook and get enough nutrition for physical effort, all while keeping costs affordable? Otherwise, where can we find inexpensive dietary supplements? Since I’m on cortisone, I have to be careful about what I eat. Thanks in advance, Aichatou
I know there are plenty of discussions on VF about the Poon Hill trek, but most seem outdated and/or don’t provide info specific to February. That’s why I’m bringing this topic back up.
Here’s my plan:
- Spending about two weeks in Nepal in the first half of February.
- Maybe extending by a few days to a week if needed.
- Heading to Pokhara—first time for my partner, second for me (I was there in September/October 1982!).
- Doing a relatively easy 4- to 5-day trek. We’re not exactly spring chickens anymore (though we’re in pretty good shape for our age).
- We don’t want to go above 3,000–3,500 meters, deal with difficult sections if there’s too much snow, or face daytime temperatures below 10°C. No problem if it drops to 0–5°C at night since we’ll be sheltered somewhere.
So, I’m wondering if the Mardi Himal trek might be too demanding for us, and if we’d be better off sticking with Poon Hill.
What do the experts think?
We're planning to go at the end of November/beginning of December to visit (with a rental car) and hike on La Palma and El Hierro for 15 full days, including 1 day for inter-island ferry transfers. What’s the best split between the two islands—8 days on La Palma and 6 on El Hierro, or even more time for La Palma? Should we have one or two home bases on La Palma? Thanks for your tips!
Annie
Hi there,
I’m looking for a family-run guesthouse in Cachaco. I read that the Monte Gordo guide service provides addresses. Does anyone have any guesthouse addresses or contact info for the natural park’s visitor center?
Thanks
Hi there,
We’re planning an 8-day backpacking trip on the island of São Nicolau. We’re torn between taking the boat from São Vicente or an inter-island flight. I’ve heard the boats don’t always run?
We’d like to make three homestay stops to travel in a star pattern from each of the three points.
First stop around Juncalinho, second stop near Cachaco, and finally a third leg near Tarrafal. We’re looking for simple but authentic guesthouses (no hotels). Any suggestions?
Thanks
Hello,
In mid-November, we’ll be in Mindelo and Santo Antão.
We’ve booked transportation with Kapverden Tours.
One trip is from Porto Novo to Ponta do Sol, including the hike from Corda to Coculi.
What’s the trail like?
Then we’ll be staying in Ponta do Sol,
Here’s what we’re planning:
A hike to Fontainhas—what’s the best direction, considering we’re not great with climbs? No problem with flat terrain or descents.
Take an aluguer to Ribeira Grande and continue along the coastal road.
With the agency:
An excursion to Cruzinha with a short walk.
Return to Porto Novo via the path from Cova to… I’m not sure where yet, to pick up the car for Porto Novo, since we’ll be taking the ferry that evening.
We’ll have a guide for this hike.
We’d love to spend a day in Tarrafal, but getting back requires a boat or taxi, and it’s really expensive!
We’re a couple, 78 and 76 years old.
What do you think of this itinerary?
I’m planning to do the Mercantour crossing following the Randoxygène route in mid-July.
I’m used to hiking in the mountains, but I sometimes get vertigo, for example on ridges with drops on both sides. I wanted to check if there are any T4 or T3-T4 sections and find out if there are any very exposed passages—and if so, where—so I can plan an alternative route.
Can anyone give me some info on this?
Thanks!
hi how can I get internet when I arrive at Haneda? I mean in areas without free wifi. Is it more interesting to buy a SIM card? If so, at the airport? thanks for your help
Hi there,
I’m planning to cross the Gourgs Blancs Pass at the end of the month, from La Soula Refuge to Portillon Refuge. On this section near the pass, I don’t have any trail marked on my IGN map. Is the path well signposted, or should I use a compass?
Also, beyond the physical effort, are there any technical, exposed, or vertigo-inducing sections on this part?
Since I’m finding very little info, I’m being thorough with my questions.
I'm developing a free and open-source web app for planning walking and cycling trips (and even car trips). You can create a route by clicking directly on the map to add waypoints, and it can consist of multiple stages. The app provides tools to edit the stages and the overall route, and to display useful information (distances, altitudes, and elevation changes). A relief profile can be shown as a graph for a specific stage or the entire route.
Once the route is ready, it can be exported as a GPX file, which can then be used with a GPS or a mobile navigation app.
The app is built in JavaScript and runs entirely in the web browser. It uses the Leaflet library and several OpenStreetMap-based services. Initially developed for my personal needs (I enjoy hiking and cycle touring), I’d be happy to share it with anyone who might find it useful. It’s free to use, doesn’t require an account, and the source code is available.
Not very well known: Hokkaido Island has national parks that rival those in North America. Hiking there is free (even many mountain huts) and requires no formalities. These treks are described in the LP *Hiking in Japan* guide—you can just buy the Hokkaido PDF. It’s way better than Mount Fuji. Of course, everything depends on the weather, which is very unstable in the Japanese mountains (frequent strong winds). The trails are often obstacle courses.
The Daisetsu Zan traverse is a stunning hike through volcanic terrain with a remote section in the middle that requires at least one night of camping (there are basic huts for the rest, which is popular with Japanese hikers): 4 to 6 days.
The Shiretoko traverse takes 2 days with views including an island in Russia, but the ridge is brown bear territory—there are even more here than in Denali National Park in Alaska (brown bears and grizzlies are the same). I ran into 7 in just 6 hours of hiking!
Hi everyone,
I’m leaving on Monday, August 3rd for my very first long-distance trek: the GR223 from Coutances to Mont Saint-Michel, over 6-7 days (~11-14 miles/day), solo.
I’m looking for tips from people who know this section well (Coutances → Regnéville-sur-Mer → Hauteville-sur-Mer → Bréhal → Granville → Genêts → bay crossing):
Budget-friendly accommodations: I’m struggling to find affordable stopover lodgings (a lot of what I find online are expensive vacation rentals, not really suited for a solo hiker). If you have any great spots (hostels, hiker-friendly B&Bs, nice campgrounds), I’d love to hear them!
Bay crossing: Any feedback on guides/providers leaving from Genêts for the final crossing?
General tips for a first long-distance trek: What you wish you’d known before your first time, pitfalls to avoid, etc.
Hi,
We’re planning to do the 4-day trek from Mestia to Ushguli without an agency. The descriptions mention that there are accommodations at each stop, but we can’t find any details about them. Has anyone got info or feedback on this route?
New to this forum, I’m planning a pretty big project for 2028.
I’m heading to Nepal to do a trek from Kathmandu all the way to Everest Base Camp (a cool 5,300 m 😄).
This trek is a bit special because even though I’ll be part of a group, I’m going solo (so far, no problem—I’m used to it). But it’s my first real trek, and it’s also a humanitarian one: once I reach base camp, I’ll stay an extra week to help clean up the waste left by tens of thousands of climbers! Since I’m originally from South America, from two countries that share the Andes, I have a deep respect for mountains—they fascinate me. So Everest… it’s kind of the trip of a lifetime!
So, a little question for those who’ve done treks to Everest before… any tips for good mental preparation (I’m already working on the physical side)?
We're planning to trek in Peru and Bolivia and would love to find some local agencies.
If you know any, could you share details on prices and, of course, the names of the agencies?
Which trek would you recommend?
Elocine
I'm heading out on a fully self-sufficient trek in Morocco (10 days) from Imilchil to Aghbalou.
Can I find screw-on gas canisters (Coleman, Primus) in Marrakech (any addresses?) or in villages between Imilchil and Aghbalou?
If not, are Butagaz canisters for camping gas (small 230g size) available?
Thanks in advance for your tips!
Hello, I’d like to embark on a little trip in my home country, Switzerland. I’ll start walking from La Cure, heading toward Le Noirmont first, then I’ll improvise my route—but it’ll probably follow the French border... at least as far as Lac de Joux.
I’ll decide day by day how much farther to go after that. My goal is to stay in nature as much as possible, wander around for as long as I can, and restock food in villages or towns along the way.
I’m thinking of mostly camping, but we’ll see if I end up in a hotel or another campsite depending on my route.
I’d love to reach La Chaux-de-Fonds on foot... maybe even Delémont.
The whole thing should take about a week, give or take.
I’ll be bringing my dog, and I’m preparing for this as soon as I’m ready.
Any tips to make sure everything goes smoothly for us? Things I should know—or avoid? What about shepherds with their flocks of sheep? And isn’t hunting season open right now?
I’m not sure if what I’m planning is even doable, which is why I’m asking around.
This’ll be my first time doing something like this—wandering in nature *and* with a dog. I’m really excited for this adventure... and I need it. Thanks!
We’re really keen on ecosystems and want to hike in "natural" ancient forests—not planted woods or areas heavily degraded by human activity. Travel guides (like Lonely Planet) don’t provide much info on this. Could you point us to the most interesting spots?
Thanks in advance for your tips.
We wish you happy holidays and a fantastic 2026, full of discoveries!
Claire and Albert
Hi, this might not be the right section, but I’d like to know if it’s possible to start mountaineering with another person without necessarily hiring a guide. We’ve done quite a bit of hiking but not mountaineering—we’ll just do a half-day glacier course. After that, we were thinking of starting with La Grande Motte and the Pointe de la Traversière, which were recommended to us. Honestly, for things like roping up and knots, I’ll learn at home with lots of videos and a book.
I’d love to know if anyone has done treks in the Rwenzori Mountains and how much it costs on average, what the infrastructure is like, the landscapes, and safety in the area. Thanks so much! I’m really looking forward to your replies.
We’re leaving in 9 days for a two-week trip to Madeira, mainly to hike.
From my research, I’ve found that since last year, access to most trails—and systematically for the most popular ones—is now paid. You have to pay an access fee of 4.50 € per person per classified hike in 2026, and even 10.50 € for the most iconic hike: Pico Arieiro to Pico Ruivo. When paying, you also have to choose a day and a 30-minute time slot for your start time. Of course, this reservation is neither changeable nor refundable, even if the weather that day is terrible.
Personally, given the massive influx of tourists to the island in recent years, I don’t mind paying a fee to help maintain the trails. Similarly, setting a limit on the number of people who can hike them per day is certainly preferable to preserve this priceless heritage.
However, what’s much less fair is that in reality, most of the available spots are reserved: 1/ for Madeira residents (which is normal); 2/ for "economic operators" (meaning local tour operators). For example, if you’re a non-resident (independent tourist), no booking is possible for the Pico Arieiro hike for an early morning start before September! So, unfortunately, we’ll have to skip this hike.
It’s the same issue for Ponta de São Lourenço, the 25 Fontes, Pico Ruivo... in short, all the most popular hikes. Oh well, we’ll skip those too!
So my question is: which hikes do you recommend where we won’t face the huge crowds that the others get? And where we can book the day before for the next day, taking the weather into account?
Finally, a quick accommodation question: we’ve booked the first week in Funchal, but I haven’t decided yet for the second week. Do you have any advice on where to stay in the south or north, preferably avoiding overly concrete-heavy and touristy spots?
I’m reposting about the logistics for Samaria Gorge.
I’d love to get recent info, especially about whether it’s possible to park my car in Omalos, do the hike, and then catch a bus back to my vehicle.
In theory, it’s doable, but when you check the KTEL website, there aren’t any feasible schedules listed. If anyone has recently organized this with reliable, verified details, I’d really appreciate it. Thanks in advance!
Hi there,
We’re flying from Montreal to Lyon this August to go hiking in the French Alps. We’ve rented a car and will be staying at campgrounds. We’re planning to do day hikes and want to stay a few days in one spot, do a few hikes, then move on to our next camping spot. Could you share your favorite spots or any recommendations for places to spend a few days with great hikes?
A few details:
We arrive in early August and leave in early September.
We’re looking for day hikes (or shorter), moderate difficulty, with a cumulative elevation gain of no more than 1000m, and of course, beautiful scenery!
We’d prefer not to drive too much—maybe it’s best not to head too far south and deal with unnecessary heat?
Along the same lines, if you know of any great campgrounds where we can start our hike directly without needing the car, we’d love to hear your suggestions!
Hi there,
I’m planning to go hiking on this island and would like to know the best time to do it. I visited for a few days in November 2018—not for hiking but just to explore—and the weather wasn’t great, especially in the mountains. So, is a star-shaped itinerary doable if I rent a car and maybe use two different accommodations?
I’m not planning to join an organized group—just traveling with one other person and organizing things ourselves—unless you’d recommend a local agency or guide. Finally, even though I’ll be getting maps, a topo guide, and a GPS, I’d really appreciate your top hiking recommendations.
Thanks so much for your tips!
I’m planning a trip around Cap Corse and the AGRIATES in 2026, from May 8th to 15th (there are still 2 spots left, by the way! Just DM me if you're interested).
I’d love to know which hikes are worth prioritizing in the AGRIATES. We’ll be staying in SALECCIA for two days as our base—what should we focus on from there?
A round trip to IGNHU beach? Any other suggestions?
For Ostricano, I think it’s too far for a round trip...
Thanks for your tips!
Have a great day,
Anie, Toulouse
I’d like to get some info about the GR10 Pyrenees traverse. I need help planning the daily stages and accommodations—my wife isn’t an experienced hiker but walks a lot, so I’d like to schedule shorter walking days and thus a longer overall trip in terms of number of days.
Could anyone give me some help and advice?
Best regards,
