UTD Decompression profile study results published

[Patoux01]

contributed to Ratio Deco 2.0, which was released last summer.

Hem, is there any chance to find the explanations of the difference between "RD" and "RD 2.0" ? I'm assuming we're talking UTD stuff there.

 

[kensuf]

Does Ratio Deco 2.0 come with a Perdix?

 

[victorzamora]

Hey Simon, thanks for all your posts, always informative. The information that was acquired during the research in Italy and from feedback of other divers diving RD after that contributed to Ratio Deco 2.0, which was released last summer.

Jay, would you care to post the ascent profile of RD 2.0 for the dive in question? I'm curious to see how it relates to other known profiles as well as RD1.0.

 

[victorzamora]

Never having received any formal training in ratio deco (or deco on the fly or whatever you might want to call it), I am a bit surprised that there can be a difference between ratio deco and something you compute with your favorite model: I was under the impression that ratio deco is not thought to be a "model" in itself but rather a mnemonic to memorize plans you compute with another model (plus small variations in depth and/or bottom time). I.e. you first compute plans in your model and then come up with simple to memorize (and reproduce in your head) ways to reproduce that plan.

This, I would have thought, would work with any underlying model (be it VPM-B or your personal favorite choice of gradient factors): You plan your dive on a computer and then memorize the plan (plus what you have to change if you go 3m deeper or stay 3min longer). But apparently at least this is not what UTD do (they seem to have RD rules that do not directly refer to an underlying model).

Let me end this with a shameless self plug: In our Theoretical Diver blog, Rick has recently written a post comparing ratio deco to profiles computed using models: Ratio Deco – is it nonsense?

My understanding of Ratio Deco is that that's how GUE uses it. There are ratios that are accepted as true (or easier to remember and otherwise close-enough) but the distribution is kinda shaped by feel based off of knowledge of a known profile or an easier-to-remember ascent path.

Talking to a GUE buddy about this profile, he had an explanation hauntingly identical to PfcAJs from a few pages ago (in terms of total stop time and how much above/below 20ft). He and AJ both said 15min stops on EAN50, so 3min stops from 70ft through 30ft. That's 5 stops at 3 minutes each, totaling the easy 15 minutes calculated previously. However, he's starting to dive higher GFLos, so he's distributing his stops differently by weighting the time closer to 30ft.

UTD doesn't teach that. As has been stated a few times in this thread, UTD teaches RD as gospel...literally as its own deco algorithm, despite UTD marketing not wanting to call it that. An algorithm is defined simply as a step-by-step set of operations to be performed. A deco algorithm is an algorithm performed to obtain deco information. UTD's RD is a step-by-step set of operations to be performed to obtain deco information....hence, deco algorithm.

 

[Remy B.]

Can I ask has formal testing of Ratio Deco 2.0 been conducted to establish its efficacy. If so has the testing shown it to be more effective or less effective than Buhlmans.

Rgds

Cathal

probably not, if I read and see in their videos it seems another arbitrary thing without scientific backup, for the science later trash their believes, then they will come up with Radio Deco 3.0, and it repeats it self all over again.

 

[Remy B.]

My understanding of Ratio Deco is that that's how GUE uses it. There are ratios that are accepted as true (or easier to remember and otherwise close-enough) but the distribution is kinda shaped by feel based off of knowledge of a known profile or an easier-to-remember ascent path.

Talking to a GUE buddy about this profile, he had an explanation hauntingly identical to PfcAJs from a few pages ago (in terms of total stop time and how much above/below 20ft). He and AJ both said 15min stops on EAN50, so 3min stops from 70ft through 30ft. That's 5 stops at 3 minutes each, totaling the easy 15 minutes calculated previously. However, he's starting to dive higher GFLos, so he's distributing his stops differently by weighting the time closer to 30ft.

UTD doesn't teach that. As has been stated a few times in this thread, UTD teaches RD as gospel...literally as its own deco algorithm, despite UTD marketing not wanting to call it that. An algorithm is defined simply as a step-by-step set of operations to be performed. A deco algorithm is an algorithm performed to obtain deco information. UTD's RD is a step-by-step set of operations to be performed to obtain deco information....hence, deco algorithm.

Lets put it like this, regardless of UTD or GUE, Ratio Deco is like driving a car with seat-belt and a normal GF is like driving a car with Seat-belt + Air Bag, a conservative GF will be like driving more slower with your seat-belt + Airbag + ABS, at the end everybody have its own ways of driving that have their consequences or not.

 

[victorzamora]

Lets put it like this, regardless of UTD or GUE, Ratio Deco is like driving a car with seat-belt and a normal GF is like driving a car with Seat-belt and Air Bag, a conservative GF will be like driving more slower with your seat-belt + Airbag + ABS.

I don't agree with that at all. The way GUE uses Ratio Deco makes a lot of sense. You plan your dive with the algorithm and software you like, you follow some rules, you get some relationships, and then you use Ratio Deco as a backup method of following the predetermined ascent profile. It's used more like backup tables than a primary computer. UTD uses RD as their only dive computer.

Relying on it instead of a computer model or full-fledged algorithm and completely ignoring the models is dumb. Pushing dives well outside the range that produces a linear(ish) and using RD without double-checking seems dumb. Using RD responsibly as a backup and sanity check is great and I think it should be taught more often, like the "rule of 130" should be taught.

 

[Remy B.]

I don't agree with that at all. The way GUE uses Ratio Deco makes a lot of sense. You plan your dive with the algorithm and software you like, you follow some rules, you get some relationships, and then you use Ratio Deco as a backup method of following the predetermined ascent profile. It's used more like backup tables than a primary computer. UTD uses RD as their only dive computer.

Relying on it instead of a computer model or full-fledged algorithm and completely ignoring the models is dumb. Pushing dives well outside the range that produces a linear(ish) and using RD without double-checking seems dumb. Using RD responsibly as a backup and sanity check is great and I think it should be taught more often, like the "rule of 130" should be taught.

I agree it shall be only used as backup, apparently it is used as the way to go by a few.

 

[PfcAJ]

I agree it shall be only used as backup, apparently it is used as the way to go by a few.

If the end result is the same then what's it matter?

 

[dmaziuk]

Lets put it like this, regardless of UTD or GUE, Ratio Deco is like driving a car with seat-belt and a normal GF is like driving a car with Seat-belt + Air Bag, a conservative GF will be like driving more slower with your seat-belt + Airbag + ABS, at the end everybody have its own ways of driving that have their consequences or not.

I car analogies: you do realise that airbags exist primarily because people wouldn't wear seatbelts, yes?