Diving tables

[gcbryan]

Perhaps here is a better car analogy: The algorithm behind your antilock brakes.

I worked for a company in the 90's that designed & built, among other things, a system for analyzing the efficiency of antilock brake systems. There are several of these algorithms out there, jealously guarded by their manufacturers, but all pretty arcane (and often tied specifically to the controller used).

Yet, this is an algorithm that is going to become life-dependingly important when you need it and you slam on those brakes - not just your own life, but your entire family in the car with you. Efficient antilock brakes can turn what would be a deadly crash into just a fender-bender, or even avoided altogether.

Do you know the specifics of your car's antilock brake algorithm? Do you even know much about the general differences in antilock brake theory and application? For most of us, the answer to both is "no", yet we trust those engineers, their algorithms and tests, and in the market itself. Does it bother you that you're entrusting your family to something so critical that you know little about? Probably not.

It's a web of trust. Same with dive computers, or tables for that matter.

That's not a better analogy. I'm not suggesting that someone understand all of the principles behind a pressure transducer but more basic than that. If you dive you should know something about deco theory. If you drive you should know something about how your car (in general) works.

You might be OK if you drive a car and know nothing about how it works. Can you argue that it's not better to at least know a little something about they way it works?

It's the same with diving. No one is arguing that you can't dive and survive without understanding deco theory. It's better if you do have a general understanding of it.

Do you really disagree?

 

[Atom]

Actually that is not true. Tables can be used to plan multilevel dives as can the erdp. They told you they could not to get you to buy more tables or a computer.

I don't remember what it is, but I seem to remember there was some info missing from the regular table to be able to do that... but I could be wrong.

In any case, I feel that just deciding to plan multi-level dives as consecutive dives with a 0min SI may be a bit foolhardy since I have no certainty if it works since I don't know how the table was produced.

And even though I don't think PADI is a charitable organization, isn't it a bit too cynical to assume that the wheel and the eRDPml exist only to sell one more table/computer? Maybe I'm just too naive....

In any case, how would you proceed about planning a multi-level dive with a table? (I'm genuinely curious)

 

[lowviz]

Perhaps here is a better car analogy: The algorithm behind your antilock brakes.
...............
Do you know the specifics of your car's antilock brake algorithm? Do you even know much about the general differences in antilock brake theory and application? For most of us, the answer to both is "no", yet we trust those engineers, their algorithms and tests, and in the market itself. Does it bother you that you're entrusting your family to something so critical that you know little about? Probably not.

It's a web of trust. Same with dive computers, or tables for that matter.

That's not a better analogy. I'm not suggest that someone understand all of the principles behind a pressure transducer but more basic than that. If you dive you should know something about deco theory. If you drive you should know something about how you car (in general) works.
..................

By my read, you guys (and I) all agree. The technical details of precisely when and with what force the automatic brakes are applied is an excellent analogy to exactly where the technical (OK, mathematically modeled) limit is placed on gas loading. There is a big difference between understanding critical braking dynamics vs. learning appropriate following distances for various speeds. Knowing something about how brakes operate and fail serves to reinforce the importance of the two sets of stopping distance tables. (ABS vs. non-ABS.) Knowing as much as you can about the complex and imperfectly understood science of bubble initiation and growth helps reinforce the importance of the tables (or computer) for your style of diving. Tables vs. computer being just different methods of tracking the math model you chose.

 

[FritzCat66]

Knowing something about how brakes operate and fail serves to reinforce the importance of the two sets of stopping distance tables. (ABS vs. non-ABS.) Knowing as much as you can about the complex and imperfectly understood science of bubble initiation and growth helps reinforce the importance of the tables (or computer) for your style of diving.

LOL! I love it. Well said. Of course more knowledge you have about a technology you're using will make you a better, more effective user of that technology - be it ABS brakes or dive computers.

But that still leaves the question I think was being kicked around here, which might be stated thus: How much depth of knowledge about ABS algorithms is necessary for a beginning driver to effectively use their ABS brakes? Analogically, how much depth of knowledge about deco theory is necessary for a beginning diver to effectively use their computer?

And separately: If a driver nowadays has no intention of driving without ABS brakes, should that driver even bother to learn about how best to use non-ABS braking systems? Wouldn't that time spent learning the non-ABS system be better spent learning more about making the most of ABS brakes and ABS braking theory in general?

Analogically, if a diver nowadays has no intention of diving without a computer, should that diver even bother to learn about how best to use tables? Wouldn't that time spent learning the table system be better spent learning more about making the most of computers and deco theory in general?

In both cases, I think the beginning user should know the basics of using the technology, even if they don't understand precisely the complete operating theory behind it; but that lack of full knowledge and understanding shouldn't be a showstopper. Examples: for a driver that means knowing the ABS brakes are not going to stop a skid in all situations; for a diver that means knowing the computer's readings are not going to prevent DCS in all situations.

 

[Thalassamania]

Let me give you an example. Most computers use pressure sensors that must be calibrated by a temperature sensor. If you don't know this but you see that the temperature reading is clearly off, what happens?

 

[RJP]

Let me give you an example. Most computers use pressure sensors that must be calibrated by a temperature sensor. If you don't know this but you see that the temperature reading is clearly off, what happens?

You win a helicopter ride!

:shocked2:

 

[Thalassamania]

Bingo. This is not a dig at computers, but rather at incomplete and inadequate training focused on computers.

 

[vjanelle]

So now that you've got me paranoid, my vytec seems to stop registering temperatures colder than 8C. Is this something I should be concerned about when diving in 4-5C water?

 

[gcbryan]

When I hear of classes "teaching the computer" it reminds me of that guy on TV selling DVD's how to use "Windows" on how to "Use the PC". It's wasted time in a class teaching someone how to read the user manual for a computer. I don't think tables need to take up as much time in class as they do either.

It's more important to learn what is behind both of them even if only in general terms.

Back to the ABS brake thing. If you know nothing about them you may attempt to pump your brakes as you would with a non-ABS system so you should know something about them.

If you are only used to ABS you may get a rental car with out it and not know how to react in icy conditions without any knowledge of non-ABS systems.

It only stands to reason that a diver should have a basic understanding of decompression just as they should have a basic understanding of managing their gas even if they have AI and punch in whatever reserve they desire.

 

[ERP]

I don't think I've ever even looked at tables since Dive 9 or 10.
I had a computer shortly after getting my C card, and I used that for a couple of dives, but my first regular dive buddy was GUE trained, and I've been using various approximations since before I took my Fundies class at about 30 dives or so.
Most of the time I still actually leave my computer in computer mode, but I don't pay any attention to the NDL.
If I were diving more than twice in a day which is very rare for me, I might use the computer as a sanity check.