Setting a dive computer for altitude diving.

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

Tom_Ivan

Contributor
Messages
214
Reaction score
194
Location
Christchurch New Zealand
There are a few mountain lakes that I want to explore that are at about 400-500m above sea level.
My dive computer's have altitude settings for diving at altitude;
A0 = sea level to 700m
A1 = 700m to 1500m
A2 = 1500m to 2400m
A3 = 2400m to 3700m

The A0 setting confuses me. If "altitude diving" is diving at heights above 300m then shouldn't A0 = sea level to 300m?
I looks to me like I should leave the computer in A0 for these lakes, But if I do it would just use the normal algorithm for sea level. It would be no different to me diving at 0m then flying straight up to 400m altitude?

Or do my computers (Mares Puk pro and Suunto Octopus 2) have an altimeter that know how high I'm starting from and make corrections? There is nothing in the manuals I could find that indicates that this would be the case and if it was, whats the point of setting the A0,A1,A2,A3?
 
Last edited:
You're probably picking up the "300m" thing from your understanding of the tables.

The decompression model in your computer will be different than the model used to generate the tables. Therefore these kinds of boundary conditions will likely also be different in the software.

R..
 
Not sure about your computers, but mine automatically know what altitude I am at and adjust accordingly. If you have to manually set your computer for altitude and given your parameters and the altitude you will be diving at, I would set it conservatively on A1= 700m to 1500m and give yourself margin.
 
The decompression model in your computer will be different than the model used to generate the tables. Therefore these kinds of boundary conditions will likely also be different in the software.
R..

So your saying that, as far as my computer is concerned, I'm not "altitude diving" until I'm above 700m?
 
All my computers adjust automatically for elevation.

So your saying that, as far as my computer is concerned, I'm not "altitude diving" until I'm above 700m?

What he is saying is that your computer uses the same calculations for all altitudes from sea level up to the 700m range before you need to adjust it to the next elevation setting.
 
Altitude is just a difference in pressure. Same as depth.

I would not recommend trying to game your computer by setting it to an altitude range setting that doesn't match the altitude you are actually at.

If you are really concerned about it, figure out if your computer has a Conservatism setting and increase that by 1.
 
  • Like
Reactions: yle
Altitude is just a difference in pressure. Same as depth.

I would not recommend trying to game your computer by setting it to an altitude range setting that doesn't match the altitude you are actually at.

If you are really concerned about it, figure out if your computer has a Conservatism setting and increase that by 1.

Its not gaming the computer it is making sure it is set properly. The Puck Pro requires the diver to make the adjustment according to the manual.

Here is what the manual states.
Atmospheric pressure is a function of altitude and of weather conditions. This is an important aspect to consider for diving, because the atmospheric pressure surrounding you has an influence on uptake and subsequent release of nitrogen. Above a certain altitude, the decompression algorithm has to change in order to account for the effect of the change in atmospheric pressure. When diving in a mountain lake, find out what the altitude is and choose the altitude range in Puck Pro within the four available options:
- A0: from sea level to approximately 700m/2300ft;
- A1: from approximately 700m/2300ft to approximately 1500m/4900ft ;
- A2: from approximately 1500m/4900ft to approximately 2400m/7900ft;
- A3: from approximately 2400m/7900ft to approximately 3700m/12100ft;
- We do not recommend diving at altitudes above 3700m / 12100ft. If you do, set Puck Pro to bottom timer and find appropriate altitude dive tables.
 
Its not gaming the computer it is making sure it is set properly.

The OP says he wants to dive at 400 - 500m. If he sets his computer to "A1 = 700m to 1500m" (as one poster suggested), that is gaming the computer.
 
- We do not recommend diving at altitudes above 3700m / 12100ft. If you do, set Puck Pro to bottom timer and find appropriate altitude dive tables.
...which pretty much don't exist.

Very high altitude diving has been very little studied, and it brings in factors that we don't have to think much about in lower level diving. I was talking to a diver who is also a specialist in high altitude decompression factors involved in NASA and Pentagon flights, and he gave me an idea of some of the considerations I would never have dreamed of. I have dived at about 11,000 feet several times, but not deep and not for long. I would not do anything serious at altitudes like that without consultation with one of the really rare people who knows something about it.
 
The OP says he wants to dive at 400 - 500m. If he sets his computer to "A1 = 700m to 1500m" (as one poster suggested), that is gaming the computer.
Actually the manual says elsewhere that if you wish to be more conservative when diving to set it to one of these "higher" settings. So I guess that Mares has decided to combine altitude and conservatism in the same setting. (Or that could be from the Suunto manual. Can't remember and also can't find it again.)

What he is saying is that your computer uses the same calculations for all altitudes from sea level up to the 700m range before you need to adjust it to the next elevation setting.
So lets pretend that I'm diving a lake that's at 650m. The A0 setting would give me the same bottom time up here as what it would give me at sea level. Am I right it saying that it would be considered dangerous to do a dive at sea level then immediately increase your altitude to 650m? Because this is essentially what I'm doing by starting at 650m.
 
https://www.shearwater.com/products/peregrine/

Back
Top Bottom