Average total dive depth to estimate your surface Gf

[tursiops]

I understand your point but precision doesn't always mean accuracy.
Your computers are indeed precise but is it not good to also have some kind of "trick" to help you to have a general validation of the numbers you are reading?
It is like having a GPS and telling people it is useless to be able to know where is the North just by being aware of the way vegetation grows.
I think all knowledge is good.

Misleading "knowledge" caused by coincidences is not good. Best to be skeptical until some reasons for the coincidences can be found.

 

[grantctobin]

Misleading "knowledge" caused by coincidences is not good. Best to be skeptical until some reasons for the coincidences can be found.

I don’t think you’ve answered RJack’s question from the other thread.

 

[tursiops]

I don’t think you’ve answered RJack’s question from the other thread.

I just did, here. I do a dive like that with two computers. Didn't seem worth saying over there because it was even farther off topic than using average depth.

 

[grantctobin]

I just did, here. I do a dive like that with two computers. Didn't seem worth saying over there because it was even farther off topic than using average depth.

The question was phrased in terms of not having access to or predating computers. You’re changing the parameters to avoid resolution.

 

[tursiops]

The question was phrased in terms of not having access to or predating computers. You’re changing the parameters to avoid resolution.

I didn't do dives like that precomputers.

 

[jale]

I didn't do dives like that precomputers.

So you mean that when you were diving precomputers time you were only doing square profiles and I suppose with a 60ft-18m/min ascent?
Well why not but it is like not daring to take your daily daytime commute road at night because there is no light.

 

[tursiops]

So you mean that when you were diving precomputers time you were only doing square profiles and I suppose with a 60ft-18m/min ascent?
Well why not but it is like not daring to take your daily daytime commute road at night because there is no light.

Using a table -- i.e., precomputets -- did not require the dive profiles to be square. Sure, you lost NDL time if the profile wasn't square, but no big deal.

 

[rjack321]

Using a table -- i.e., precomputets -- did not require the dive profiles to be square. Sure, you lost NDL time if the profile wasn't square, but no big deal.

So basically you are dissing on people way more experienced than you who are or were actually DOING 100ft max, 63ft average, 105minute cave dives with sawtooth profiles and coming up with deco schedules from tables or software that work without 45mins of deco. In fact, its about 1/4 that time - kinda magically similar what your two computers report. Some of us were doing that 10 years before Shearwater existed and not on a Nitek-He either.

 

[PfcAJ]

So basically you are dissing on people way more experienced than you who are or were actually DOING 100ft max, 63ft average, 105minute cave dives with sawtooth profiles and coming up with deco schedules from tables or software that work without 45mins of deco. In fact, its about 1/4 that time - kinda magically similar what your two computers report. Some of us were doing that 10 years before Shearwater existed and not on a Nitek-He either.

Did it all the time and I’d do it today without a computer.

Magic.

 

[tursiops]

So basically you are dissing on people way more experienced than you who are or were actually DOING 100ft max, 63ft average, 105minute cave dives with sawtooth profiles and coming up with deco schedules from tables or software that work without 45mins of deco. In fact, its about 1/4 that time - kinda magically similar what your two computers report. Some of us were doing that 10 years before Shearwater existed and not on a Nitek-He either.

Look, there are always going to be folks on the bleeding edge of best practices.....if you and some of the others function that way, fine.
What I'm skeptical about is broad statements to the rest of the diving community that using an average dive depth with tables designed for use with a maximum dive depth is a good practice. You and others argue it is because you are doing it; I argue it is not because it has no rationale other than it seems to work most of the time, in some situations, with the counter argument that on-gassing/off-gassing is determined by exponential processes but the depth-averaging assumes they are linear.
Can these points of view be brought together?
(1) Turns out many (most?) view depth-averaging as meaning the average depth of the bottom (or of the maximum depth of the dive), NOT the average depth of the entire dive. Well, OK. I see the principle involved, it is called a tangent-linear approximation. You take a curve (in this case, an exponential) and fit a straight-line tangent to it and then work along that straight line. That is justified, can certainly work within some limits, and I take no issue with it.
(2) For those who insist that the average depth of the dive produces the same deco considerations as does following the actual dive profile, and use some examples to show that it is true, I can only say that it is also easy to produce counter-examples where it is not true, as in some previous posts. The logical fallacy here is that if you want to show something is true, you have to test ALL the cases, where if you want to show something is false, you only have to find ONE false case.
(3) By the way, you are quite correct, I do not have as much cave-diving experience (15 years or so) or deco experience (20 years or so) as many of you. But that is not an argument in favor or your position, rather it is an argument against me as a person. Not allowed on SB, and reportable.

There is a lot of hand-waving and name-calling in technical and deco diving. I can only assume that is because there are no valid arguments to back up all the assertions. It is the worst kind of discussion: a question is raised, an ad hominem attach ensues.

My assertion is that tables designed for use with maximum depth of a dive cannot validly be used with the average depth of a dive, without some additional caveats and adjustments. No attack on me changes that, and there are peer-reviewed articles available (linked earlier) to back up that assertion. Sure, you can find many examples where such use may be "close enough." The problem is you can find many examples where it is NOT close enough. Best to be skeptical.