1000m Altitude dive : how to plan it ?

[milkathecow]

hi,

I have done my Fundamentals and Tech 1 and am coming up with a question which is clearly crossing my mind.

I have a lake in the mountains in mallorca... and i have been aching to go up there for the last 2 years since we have moved (yes salt water vs fresh water... need the fresh).

My main issue is the following. If i am going to do that dive, i want to do it the DIR way, no other seems safe to me to do it properly.

The lake is at 970 meters of altitude above sea level. therefore tables and ordinary values are not accurate for deco procedures or ascent speeds.

Could anyone tell me how they would plan it ?

Max depth for first dive 20-25m, dive time 50-60mn. Obviously i would do it on 32%.

thanks in advance for your answers.

If this is the wrong place as it's my first post in this section... please feel free to move it, just let me know where you put it so that i can find it again .

 

[iowasnowboarder]

In Colorado, we have been diving the high mountain lakes, up to about 10,000ft, without adjusting anything...

 

[mer]

Deco Planner/File/Dive Plan Preference. Both Buhlmann and VPM have a place where you can enter the altitude or surface pressure. Only VPM has a way for you to tell it how long you've been at altitude, so I would run both and compare the profiles.

I haven't been doing dives at much more than a couple hundred feet of altitude, but this is how I would plan them. Just like our Tech 1 rules of thumb send me back to the tables for dives repetitive deco dives, deco dives followed by rec dives, or dives away from the set points, I'd consider altitude one of those things that would send me doing a little Decoplanner table wacking before deciding on final profiles.

I would definitely add some time in the 10' to surface ascent.

 

[RTodd]

Altitude correction factors are something you can get from PADI. Nothing special about it. As recommended above, just put it in Decoplanner and analyze what the differences from a below 300m altitude dive would be. It probably isn't significant enough to really change much.

 

[amascuba]

I'm with Michael, I typically dive at altitude ranging in the 4000 - 6000 ft range and I don't adjust my dive plan for altitude. If you wanted to add conservatism to your dive you could follow these rules:

• Every 1000ft. above sea-level is 4%.
• Round up to the nearest 1000 foot.
• Formula: Depth x 1.Altitude% = ACDepth

The formula is in imperial, but it shouldn't be too hard to convert to metric. I believe that 1000ft is about 305m.

For example:

My dives are typically 4600ft above sea-level and around 80ft deep. I would round 4600ft up to 5000ft. 5000ft = 20% (5 x 4). So I would do 80ft x 1.2 = 96ft.

Side note: I've done that dive on 32% with 40 minute bottom times, followed by a minimum deco ascent with out any complications.

 

[rjack321]

1000m really isn't very high. The Califonia guys do both tech1 and recreational dives in Lake Tahoe (which is about 1,900m) and just add a few extra mins at the 6 and 3m stops. Actually I hope most of us do more than "minimum deco" when we can. Unless there's a problem there's no rush to get out of the water.

To put it into perspective 1000m of altitude = ~1.5m of water, not much pressure.

 

[milkathecow]

Thanks a lot guys for the little informations. i usually dove in switzerland, but more in lake geneva which is approx 400m altitude, and now i'm at sea level, sor for me it would be a novelty to go up to 1000m to take that dive . I will check and extend my usual dive or basic deco time but if i freeze my ass off i'll just limit bottom time .

Thanks for the tips and clues, i like the simplicity of the 4% one i must admit... allowing me to think and calculate by myself is something i treasure in the DIR process.

rjack, put in that way for perspective... you're absolutely right, hadn't thought about it on that point of view, thanks

 

[amascuba]

Thanks a lot guys for the little informations. i usually dove in switzerland, but more in lake geneva which is approx 400m altitude, and now i'm at sea level, sor for me it would be a novelty to go up to 1000m to take that dive . I will check and extend my usual dive or basic deco time but if i freeze my ass off i'll just limit bottom time .

Thanks for the tips and clues, i like the simplicity of the 4% one i must admit... allowing me to think and calculate by myself is something i treasure in the DIR process.

rjack, put in that way for perspective... you're absolutely right, hadn't thought about it on that point of view, thanks

The 4% rule is simple. The general theory is that for every 1000ft/300m above sea-level the atmospheric pressure is 4% less. It correlates with PADI altitude correction tables. I generally don't compensate for altitude, but I teach it quiet a bit when I'm working as a divemaster for my LDS.

Here is my last dive profile doing the dive that I listed. The average depth was basically 70ft at the bottom portion of the dive.