UTD Decompression profile study results published

[UWSojourner]

I disagree: the study proved that "AG's lucky rabbits feet UTD Ratio Deco(TM)" schedule is not as efficient as a GF 30/80 schedule. It sheds no light on ratio deco as a methodology.

Just in case there was confusion: the ratio deco type 2 from my post that you quote above has nothing to do with "UTD Ratio Deco 2.0(TM)". I'll edit my post to type X and type Y to make that clear.

The rest of your post is more about philosophy and preference, which I have no wish to argue with.

I said the study "provided evidence". Certainly the people doing the RD profile thought the RD profile was "really great". Just listen to their justifications. A lot of technical justification, but when actually measured??? Clearly it wasn't as good as a run-of-the-mill GF profile (even a GF profile with LESS time!!).

So I guess you're saying "MY really-good-appoximation is better!" Ok. I guess. Evidence????

My guess is your on-the-fly approximation is roughly the same. Probably does a good job sometimes. But probably equally as bad sometimes.

 

[elmo]

I can see that. But are there more reliable and more accurate methodologies?

For example, consider tables. If you bring tables:

...

This new study provided evidence that a "well planned RD schedule" is not as good as a properly planned dive. And IMO RD 2.0 = another-on-the-fly-approximation-2.0.

Is RD best practice? Of course not.

"Best practice" is subjective. Is it the most efficient decompression in a pure sense, or does it consider other elements of planning and executing a dive? I use (and contribute to) decompression software, and have no problem with carrying tables. But many of us can get a good approximation of a Buhlmann decompression profile that is valid over the range of dives we commonly do, and simple enough to remember without tables, and simple enough to vary for minor adjustments in depth and bottom time. I do that, and I call that ratio deco. Reading this thread, and GUE SOPs and training manuals, indicates that I am not alone.

For clarity, and to avoid misinterpretation, the study does not establish GF 30:85 as optimal decompression. It simply indicates an advantage for that algorithm over one which places more emphasis on deep stops.

This study is definitely interesting, and as Simon Mitchell stated, the compared RD profile appears less than optimal. But the tested "RD" profile bears no resemblance to the ratio deco profile that I would use for a 50m dive. I would not be stopping so deep, and I definitely would not be switching to back gas at 9m.

 

[Patoux01]

I said the study "provided evidence". Certainly the people doing the RD profile thought the RD profile was "really great". Just listen to their justifications. A lot of technical justification, but when actually measured??? Clearly it wasn't as good as a run-of-the-mill GF profile (even a GF profile with LESS time!!).

So I guess you're saying "MY really-good-appoximation is better!" Ok. I guess. Evidence????

My guess is your on-the-fly approximation is roughly the same. Probably does a good job sometimes. But probably equally as bad sometimes.

Sigh. No. You just won't understand what RD is.

 

[huwporter]

I said the study "provided evidence". Certainly the people doing the RD profile thought the RD profile was "really great". Just listen to their justifications. A lot of technical justification, but when actually measured??? Clearly it wasn't as good as a run-of-the-mill GF profile (even a GF profile with LESS time!!).

So I guess you're saying "MY really-good-appoximation is better!" Ok. I guess. Evidence????

My guess is your on-the-fly approximation is roughly the same. Probably does a good job sometimes. But probably equally as bad sometimes.

The people who did the profile in the study thought it was going to be proven really great because a) it had a bunch of extra deep stops added, b) it had an 'oxygen window' s-curve, c) it had a backgas break at 9m (after a stop at PPO2 1.1...), not because it was a 'ratio'.

Again, don't confuse "UTD Ratio Deco(TM)" with any methodology for approximating profiles. They weren't claiming superiority because it was an approximation of anything, they were claiming superiority because of all of the things they did to make it different. (And they were clearly mistaken.)

 

[UWSojourner]

The people who did the profile in the study thought it was going to be proven really great because a) it had a bunch of extra deep stops added, b) it had an 'oxygen window' s-curve, c) it had a backgas break at 9m (after a stop at PPO2 1.1...), not because it was a 'ratio'.

Again, don't confuse "UTD Ratio Deco(TM)" with any methodology for approximating profiles. They weren't claiming superiority because it was an approximation of anything, they were claiming superiority because of all of the things they did to make it different. (And they were clearly mistaken.)

I know. You can't say all on-the-fly-guesses are bad just because you showed one on-the-fly-guess is REALLY bad. Arguing religion is not generally productive.

But at some point (and I think most rational divers are there) divers will say they want EVIDENCE that huwporter's RD is really better in terms of outcomes than the RD that was just tested. Think --- huwporter has a certain rationale ... but so did the RD that was tested. Is huwporter's better???? Maybe. Or maybe all wild-ass-math-guesses are uncertain.

Is RD best practice? I doubt it.

 

[Patoux01]

With all due respect, stop talking ****. This is not religion, RD is a METHOD to obtain THE SAME deco schedule as WHICHEVER deco algorithm YOU have decided to build it against. The real RD does not claim to be better than other algorithms, it's trying to emulate them!

 

[huwporter]

snip

OK dude, you seem so keen to argue you aren't reading what I actually wrote. I'm out.

 

[UWSojourner]

With all due respect, stop talking ****. This is not religion, RD is a METHOD to obtain THE SAME deco schedule as WHICHEVER deco algorithm YOU have decided to build it against. The real RD does not claim to be better than other algorithms, it's trying to emulate them!

I understand. Ratio deco helps you remember.

But if it helps you remember "closely", then you are trusting that the difference isn't important? The recent study said the difference was important

 

[Patoux01]

No. The recent study said "something radically different is not as good". The tests here were testing the "UTD-thing (Tm)", not "does it matter how we compute an ascent plan?". The UTD-thing DOES NOT try to emulate any known algorithm.

Edit: I'll explain a bit more what I mean with "does it matter how we compute an ascent plan?"" I could compute a deco schedule by hand using Buhlmann algorithm, then I could implement it on Matlab on my 64-bits computer, and then I can do it on an 8-bit mcu. Do you think the end result are gonna be dramatically different? The errors are gonna be in the "close enough" range. What RD (the methodology) tries to do is to make something that lands in the "close enough" range. What UTD-thing tried to do is "Lol, physics? Who needs that. I'm just gonna put some here, and there, and some more here, all good that's the best we can do".


P.S: RD is just "trying to find a simple link between decompression time and bottom time", which, as long as we are calibrating it with enough setpoints, will always be "good enough", it's the same thing as a mathematical approximation of a function by its tangent, it's good enough as long as you don't go too far from the setpoint (hence the different ratios, the restrictions on gas in the "official" versions, etc. but anyone could make it work for air and Nx80 if he wanted, it just takes some simulations and a bit of mathematical background to easily understand it). UTD is not doing that.

 

[UWSojourner]

No. The recent study said "something radically different is not as good". The tests here were testing the "UTD-thing (Tm)", not "does it matter how we compute an ascent plan?". The UTD-thing DOES NOT try to emulate any known algorithm.

Ok. If you are saying RD just helps you remember GF50/X, or VPM-B+x then I guess I would say ... why remember??

If you believe GF50/x or VPM-B+X is the best profile, why not carry tables for the schedule you want to follow? Maybe even carry computers AND tables for that profie?

What makes you think that a diver can compute the optimal profile "on the fly". It seems to me more studies would show a deterioration of mental output under stress.

Is RD best practice? I doubt it.