Poll: Algorithm Type - strong views/preferences?

[boulderjohn]

Just a note for clarity - "Conservatism" is a pretty bad descriptor for these things, as limited NDLs or longer deco don't actually make the dive "more conservative." There was a fairly recent study done where two dives were done and the algorithm with 44% more deco time was notably worse than the other.

I agree and even started a thread on this problem some time ago. In decompression algorithms, the word "conservative" is associated with staying deeper longer on your ascent. This is opposed to an "aggressive" profile that has you ascending to shallower depths earlier in the ascent. This implies that a "conservative" profile" is SAFER than an "aggressive" profile. Stating this overly simply, research is indicating profiles that leave you deeper longer do not do as well as profiles that get you shallower sooner.

In terms of decompression, the word "conservative" does not necessarily equate to "safer."

 

[Freewillow]

@bolderjohn, thank you for the link. This is what I tought. The old rossh story about deep stops.

 

[boulderjohn]

@bolderjohn, thank you for the link. This is what I tought. The old rossh story about deep stops.

No--it goes well beyond that.

Here is the announcement of the actual study: UTD Decompression profile study results published

This study compared the UTD version of Ratio Deco to a Bühlmann profile with gradient factors. The UTD Ratio Deco study did very poorly in that comparison. That was the study that was referenced above.

 

[victorzamora]

what is the link to this study? Thanks

@bolderjohn, thank you for the link. This is what I tought. The old rossh story about deep stops.

No--it goes well beyond that.

Here is the announcement of the actual study: UTD Decompression profile study results published

This study compared the UTD version of Ratio Deco to a Bühlmann profile with gradient factors. The UTD Ratio Deco study did very poorly in that comparison. That was the study that was referenced above.

Thanks for the answers, John. That's exactly what I was referring to.

Let me say, though, that I certainly don't think this is the place for that convo and I didn't mean to start it. I just used it as an example to prove that "more conservatism" isn't actually more conservative.

 

[Kharon]

... There was a fairly recent study done where two dives were done and the algorithm with 44% more deco time was notably worse than the other.

Since I never get a deco obligation, I don't see how this applies to me.

 

[aquacat8]

How about DSAT for safety? My Oceanic is DSAT and I notice not many computers are anymore. Does anyone know why that is? I want a back up watch and I'm thinking I need Oceanic ( like a Geo2) but with the Huish buy out and the difficulty I had recently buying my Pro Plus 2 that replaced my Pro Plus I'm afraid Oceanic might disappear. And if that happens maybe DSAT will disappear as a computer option. Is DSAT outdated and risky or tried and true, like aspirin vs ibuprofen?

 

[MikkelBC]

I bought my computer for the features and large display. As long as I can adjust it to be conservative (since I'm 71) I'm happy.

I just bought a new dive computer and since I previously used an Uwatec Galileo Sol, I narrowed down my choice to be between the Scubagro G2 and Shearwater Perdix AI.

I also want to be able to "adjust it to be conservative". In fact, I find that to be important. The Shearwater offers gradient factors for that and the Scubapro offers something they call MB levels. The problem with MB levels is that I don't know what they mean. I was not able to easily find an explanation of how (and how much) the settings will affect my profile. I have no clue whether to use MB0, MB1, or whatever. Gradient factors are well defined and explained.

This characteristic was the deciding factor that made me chose the Shearwater computer. Because I want to be able to adjust my conservatism setting in a way that I understand.

 

[victorzamora]

Since I never get a deco obligation, I don't see how this applies to me.

The post wasn't meant as targeting you or your diving specifically, just the validity of that phrasing. It's a pet peeve of mine that is the fault of the manufacturers/industry.

But every dive is a deco dive, right? So the behavior of the algorithm, especially on repeat dives over long trips, dives close to NDLs, behavior of the algorithms on fast ascents, altitude, etc, is certainly subject to that same problem. My example regarding the decompression test was simply that, an example.​

 

[Dan_P]

Just playing with semantics; you could argue that stopping deeper and spending more time shallow would technically be a more "conservative" approach, but a less "effective" one.

"Conservatism" settings on a given computer, by that logic, ought sacrifice effectiveness for a reduced risk of a hit - thus completing a logic paradigm where "conservative" and "effective" are mutually contradictory, at least to some extent.
If the above holds true on a given computer's algortihmic rendering under added "conservatism", i.e. when adding conservatism level, it tells you to stop deeper as well as stay shallow longer, then the above logic may well be the reason for the choice of phrasing - "conservatism", that is.

If that is the case, then added "conservatism" is compatible with deeper first stops, logically speaking.

 

[Kharon]

The post wasn't meant as targeting you or your diving specifically, just the validity of that phrasing. It's a pet peeve of mine that is the fault of the manufacturers/industry.

I guess I should have said - I have no idea how what you are saying applies to me. In other words I'm confused. The Icon uses a RGBM model and I've been told that it's very conservative - some say too conservative.

Is this an issue for me? - in other words less effective and somethig I need to be aware of? I don't spend much time deep on any dive and most of my time is spent above 60'. Average depths range 20-40 something.​