PADI tables vs TDI/USN tables vs Dive Computer

[J-Vo]

I think you are replying to shurite7's post, Josh, in which case you may have misunderstood it. He did not say he used the wheel to understand decompression; he used it to understand planning a multi-level dive. When planning a multi-level dive with the wheel, you planned 3 maximum depths, say 100 feet, 70 feet, and 50 feet. Then you figured out how long you could stay above each level and still stay within decompression limits. That is a type of planning that is rarely done on NDL dives. Yes, we do it on decompression dives using desktop software, but people don't do it on NDL dives.

Your probably correct. It just annoys me when people think the table imbibes some greater understanding of decompression theory then a PDC. Or worse that the PDC simply works the tables for you.

 

[Wibble]

It's not a rant about Bullhman being better; it's about it being somewhat standard and widely adopted as the algorithm's pretty much open sourced. There's little that is more irksome than having to end a dive early because the algorithm someone's using doesn't match that of other divers**. Similarly certain algorithms are only available from one source, so no decent planners.

eRDP, the slide rule, cutting tables, proprietary tables, deep stops... all things from the past.

And for the original poster who may make the move to technical diving, it's a lot easier if you understand one algorithm and how to 'tweak' it for your personal circumstances (gradient factors).


** although nowhere near as annoying than when some tight-fisted diver is on air whilst others are diving Nitrox and the tight-wad (divemaster) ends the dive early.

 

[tursiops]

It's not a rant about Bullhman being better; it's about it being somewhat standard and widely adopted as the algorithm's pretty much open sourced. There's little that is more irksome than having to end a dive early because the algorithm someone's using doesn't match that of other divers**. Similarly certain algorithms are only available from one source, so no decent planners.

eRDP, the slide rule, cutting tables, proprietary tables, deep stops... all things from the past.

And for the original poster who may make the move to technical diving, it's a lot easier if you understand one algorithm and how to 'tweak' it for your personal circumstances (gradient factors).


** although nowhere near as annoying than when some tight-fisted diver is on air whilst others are diving Nitrox and the tight-wad (divemaster) ends the dive early.

LOL. If you love it so much, at least spell it right.

 

[Wibble]

LOL. If you love it so much, at least spell it right.

Which is why it's often referred to as ZHL (Zurich airport)

Specifically ZHL16-B+GF

We do agree on Deco For Divers (Powell) where it's nicely introduced and explained; essential reading for advanced nitrox and decompression procedures training.

 

[boulderjohn]

Your probably correct. It just annoys me when people think the table imbibes some greater understanding of decompression theory then a PDC. Or worse that the PDC simply works the tables for you.

...and I fully agree with you on this.

You are describing a problem that comes from the fact that in early scuba training, it is common for people to teach decompression theory and how to plan for decompression using tables at the same time, leading some people to believe that those two separate concepts cannot be taught separately. That includes many instructors who have never done it any other way.

When I taught OW classes, I developed a pretty good presentation (later including animated powerpoint) showing how tissues on-gas and off-gas and why decompression was necessary. Later on in the course, I showed students how to use tables to plan the necessary decompression. When the course changed to teach computers rather than tables, I did it all the same way, showing how computers did the decompression work at the same point I used to teach the tables. In both versions of the course, the students got a thorough understanding of decompression first, followed later by instruction on how to manage it.

 

[boulderjohn]

Was trying to remember what DSAT was. It's a PADI mob called "Diving Science and Technology" which developed the Recreational Dive Planner (RDP) beloved of PADI.

Must be better than Bullhmann as it was developed afterwards (standing on the shoulders of giants). Or maybe it's just a "special" algorithm that works for a small subset of diving conditions, rather than the more general algorithm developed by Bullhmann.

In addition to what Tursiops wrote, especially about the fact that the DSAT work was published at about the same time as Buhlmann's work and was based on completely separate research, I would like to point out what was said earlier--the PADI RDP was created because of the limitations on recreational diving imposed by the use of the US Navy tables. A diving scientist, Dr. Spencer, was frustrated by both the long surface intervals and the fact that the dive had to be measured by the deepest portion, even if only a few minutes had been spent there. His frustration led to the research that developed the RDP, which dramatically lowered surface intervals, and the wheel, which allowed multi-level diving. The research they did was published.

If you go to the Ask Dr. Decompression forum on ScubaBoard and check the threads from the earliest days of ScubaBoard, you can find some clear references to that history. Dr. Decompression then was Dr. Michael Powell, a NASA decompression scientist who was on the team that created the RDP. In the earlier days of ScubaBoard, he answered questions about decompression, and he was active in that role until he retired from ScubaBoard a surprisingly short time ago. I specifically remember him describing his frustration trying to understand the fact that some people bubbled so much easier than others and his inability to prove his hypothesis that exercise-generated micro-bubbles led to bubble formation.

 

[dmaziuk]

Was trying to remember what DSAT was. It's a PADI mob called "Diving Science and Technology" which developed the Recreational Dive Planner (RDP) beloved of PADI.

Must be better than Bullhmann as it was developed afterwards (standing on the shoulders of giants). Or maybe it's just a "special" algorithm that works for a small subset of diving conditions, rather than the more general algorithm developed by Bullhmann.

Define "better". DSAT's optimized specifically for repetitive no-stop diving, for "recreational" users. The flip side it's "worse" for deco dives. ZH-L16 is general and open which makes it "better" for planned decompression dives: you get more dive planners matching more users' computers and so on.

And then there's projected DCS incidence: M-values are tuned to produce X cases of clinical DCS in 100,000 dives and the X that's "better" for the Navy is not necessarily good for me.

 

[Wibble]

I specifically remember him describing his frustration trying to understand the fact that some people bubbled so much easier than others and his inability to prove his hypothesis that exercise-generated micro-bubbles led to bubble formation.

One of the perennial challenges of decompression science is understanding why and how it works; we know it works, but there's too many "undeserved bends" -- those people who've followed a gentle dive profile yet still get DCS.

Define "better". DSAT's optimized specifically for repetitive no-stop diving, for "recreational" users. The flip side it's "worse" for deco dives. ZH-L16 is general and open which makes it "better" for planned decompression dives: you get more dive planners matching more users' computers and so on.

Bhulmann has the same concept as the decompression (which is for ALL dives, recreational or 'technical') abates whilst off gassing (decompressing) during the surface interval.

And then there's projected DCS incidence: M-values are tuned to produce X cases of clinical DCS in 100,000 dives and the X that's "better" for the Navy is not necessarily good for me.

All decompression algorithms are statistically tweaked; that's all part of the development.

Gradient Factors allow some control over the dive profile which one would adjust to the day. Some computers will also show your surfacing GF (i.e. the GF if you ascended now). We all know that a young and fit navy person would probably handle higher decompression stresses than an older, unfit person (typical on dive boats), hence moderating the gradient factors one uses.

 

[dmaziuk]

We all know that a young and fit navy person would probably handle higher decompression stresses than an older, unfit person (typical on dive boats), hence moderating the gradient factors one uses.

That would be one of the differences between deco for divers and deco for comp. sci. geeks: the latter don't consider "we all know" a valid argument, nor that tweaking the limits (via gradient factors or some other means) would necessarily help the feeble and infirm.

 

[tursiops]

Bhulmann

Bühlmann. You are getting closer.