Diving tables

[Dr Neil]

Other - I plan and dive with a computer. However, I use tables to plan enriched air dives. I use a wheel just because I want to be one who can claim to know how to use one.

When I teach Tune-Up courses, dive table review is always a part of the class portion of the class. Most divers coming in for a refresher do not dive with a computer so I take the extra time to review the RDP with them.

 

[chs8084]

I learned the tables and tried for a while after I got my computer to use them for planning and checking the computer, but like many others, the computer said and I was fine and because the tables for square profiles don't account for my diving profile, they have reached a point of ceasing to be useful. I am new to nitrox, so I am still checking on those dives.

 

[Tigerman]

I voted "other", because its not that straight forward.

For "vacation diving" I generally dont use the tables much because I have an idea of what I can do and be within the limits as well as how my computer will correspond with it.

For my local dives I ALWAYS plan and conduct my dives from tables and gas consumption as they are almost always solo dives and I dont want to push my luck on those.

 

[Thalassamania]

As far as recreational diving is concerned, I've mentioned elsewhere that I think learning tables even for basic OW is a complete waste of time, and I applaud SDI for abandoning them for basic OW. More agencies should follow suit.

All the anecdotal stories folks use on the board to show how bad & incompetent people are in understanding what their computers are displaying do NOT make for an effective argument for using tables - but they do make a GREAT argument for why more time should be spent training on their particular computer and less time learning a technology they will not use in the real world.

The FCC now no longer requires learning Morse for a basic radio license. Lots of old-timers continue to berate that decision. But I think it was a good one, and over time the old-timers are largely being ignored. You simply don't need Morse to run voice or Packet. Same should happen with dive instruction for basic recreational dive certification and tables - ditch the old tech, leave it for more advanced enthusiasts to learn later if they want.

Techies and decompression divers are a completely different animal and might prefer tables for certain operations. But most divers are strictly recreational.

It doesn't really matter if people use tables or computers to control their dive, the problem is that they likely have no clue as to the model behind it. A table is naught but a series of snapshots of the model, and a computer is only a cartoon of the model ... it doesn't matter a hoot which you use. The problem with computers is that they are being used like stop lights ... green means go, yellow means caution, red means stop. That's all a lot of people are getting in their classes, and yes, while less likely, the same can occur with tables. Exposing ones self to a hyperbaric environ has significant risk associated with it. People should not be expected to take such risks without being able to provide an informed consent. The "red light, green light, one, two, three" approach to decompression management moves away from any sort of real informed consent into the range of little more than, "trust me."

 

[Diver0001]

Thanks, everybody who answered. I'm really amazed at the number of people who still use tables in some fashion.

In practice I still see the odd person who uses tables but they're invariably people who intend to buy a computer but haven't gotten around to it yet.

2 weeks ago I was doing guided diving with someone using tables and they told me that they were on such a tight budget that they had to choose between diving with tables and not diving. I think these cases do need attention and there are reasons to teach tables optionally for people who choose to use them.... but for the "average" diver who can afford a computer, the tables are essentially useless.

I should just say that I don't have anything against tables. I used them for 15 years and was probably one of the last kids on my block to buy a computer. Even today I seldom refer to the data on my computer unless the dive is going to put us in deco, but that's just me. Nevertheless, I do believe it's an essential tool for most divers.

R..

 

[Jim Lapenta]

I began with tables, bought a comp early, then went back to tables after taking some tech training. ANd while I use a comp now it is a back up. All training dives are done with tables from OW on. And it is because of Thal's analogy. I did the green, yellow, red. And then began to see just how stupid that was. I don't know if the algorithm in the comp is based on a 50 yr old, slightly overweight but still in decent shape, male. Also I do actually try to stick with a square profile as much as possible. That is just me. It used to be about the amount of bottom time. Now it is about the quality of that time.

I would dive my computer and take it right up into the yellow as many new divers do thinking that it was ok as long as I stayed out of the red. But how much out of the red was safe for me? Those who do this can you say specifically how much time YOU have before the comp goes into the red and will be ok? The same that the 25 yr old swim team member does? Or more than the 60 yr old fat guy who has BTW been diving for 30 yrs? Truth is you don't. Mortality is a tricky thing that will sneak up on you. If you're willing to risk that an electronic device is safer than something you can run a truck over and will still work coupled with your brain and common sense all well and good. I just will find someone else to dive with. If you want to back up your brain with a comp that's ok. Just don't substitute it for that brain.

 

[seaducer]

I use tables to plan dives, but generally will execute the dive with a computer.

If I know the profile will be square sometimes I will leave the computer in a pocket (I like the logging feature) and dive the old way, table, time and depth gauge.

Knowing tables, and diving them long before I got a computer helped me to understand what my computer is doing. I do not believe I am blindly following my computer.

I admit I have kind of a thing for tables. I hope people here may understand that. I have tables from agencies I haven't taken classes from, though I do not actually use these tables. They are just for show. Some day my collection may be worth money. Or maybe it will just prove I am old and crotchety.

 

[FritzCat66]

The problem with computers is that they are being used like stop lights ... green means go, yellow means caution, red means stop.

Yet if the algorithms themselves really were completely accurate, that's exactly what you would expect to be able to do: green-yellow-red. But of course the algorithms aren't completely accurate; yet that's not the computer's fault, it's a limitation of the current science.

However, if increased chances of DCS while using computers properly were indeed a real problem, I think we would have seen the statistical results of that DCS increase by now, given that practically everyone uses them, but AFAIK that isn't happening. (One could probably measure this by counting up "your device caused undeserved DCS" lawsuits against the computer manufacturers relative to the number of computers they sell.)

I attended a recent DAN seminar on DCS sponsored by my LDS and the representative indicated there isn't data to support the claim about computers being riskier for DCS one way or another, but he did say that there seems to be a statistical drop in the number of diver embolisms since computers became widespread, which he attributed not to computers' nitrogen absorption/offgassing calculations but rather more likely simply due to their ascent alarms.

Yet, even if it does turn out that more people are getting DCS following their computers than following tables, that's still not a particularly good argument for going back to teaching tables; it just makes it all the more apparent that we should spend more time on using computers correctly and using them conservatively, and perhaps it might also be a good argument for getting the computer manufacturers to make them more conservative for us (and to keep up with the science).

The DAN rep did discuss the various algorithms currently used by the computers (and tables), however, and the fact that there are still lots of unknowns regarding decompression theory - pointing to the number of "undeserved hits". The DAN rep thus encouraged everyone to be very conservative about nitrogen, whether using tables or computers, because both are simply expressions of mathematical and theoretical models. I think this is sage advice.

 

[Thalassamania]

Fritz, though you quoted me, you did not address my post but rather made some pitch for the "safety" of computers, which I never said were or were not "safe."

Please reread and speak to the questions of "informed consent" and the morality of exposing someone to hyperbaric conditions that they have no grasp of.

It doesn't really matter if people use tables or computers to control their dive, the problem is that they likely have no clue as to the model behind it. A table is naught but a series of snapshots of the model, and a computer is only a cartoon of the model ... it doesn't matter a hoot which you use. The problem with computers is that they are being used like stop lights ... green means go, yellow means caution, red means stop. That's all a lot of people are getting in their classes, and yes, while less likely, the same can occur with tables. Exposing ones self to a hyperbaric environ has significant risk associated with it. People should not be expected to take such risks without being able to provide an informed consent. The "red light, green light, one, two, three" approach to decompression management moves away from any sort of real informed consent into the range of little more than, "trust me."

 

[oldogre]

As someone with only 40 dives, I have never dived a "square profile". So I find a computer safer than mental arithmetic using memorized tables. Yes every dive is planned, but there always variables e.g. current & surge.