PADI tables finally going away?

[EastTNDiver]

One more post in the countdown (countup?) to 1000...


I agree entirely that it's important to understand the "why's". But how does tracing your finger along a line on a table teach the "why" any more than pushing buttons on a computer? Instructors have been teaching the theory and illustrating it with the data on the tables for so many years that in the minds of many tables and theory have become confused as being one in the same thing. They are not. Both the data on tables and the data on computer displays are the result of calculations based on the theory. Neither tables nor computers are the "why." One way to work towards divers not simply "listening for the beep" is to actually instruct them in the use of their computers so that they know what functions are available and get them into the habit of accessing these functions for dive planning before they hit the water.

I guess because the instructors I've had did a lot more than "tracing your finger along a line". I agree that if that is all the instructor is doing, then you're not learning what you need to know as a diver. As for teaching the student his computer, I'm assuming they are learning the computer available from their training facility, with the rare student possibly purchasing one before training. What happens when they actually purchase their own computer, and its operation is quite different? I have two computers from the same manufacturer, and while their algorithms are identical, their operation isn't even close.

One of the things that happened in my classes, is that working the tables was drilled so thoroughly that the NDL's almost became second nature. While the square profiles taught with tables do not correspond with the multi-level profiles allowed by computers, knowing the information behind the algorithms can allow for better decisions underwater. I agree that computers should be stressed much more than they are, and I'm guess'timating that will happen soon...curriculum changes tend to lag behind market saturation in any given industry. However, I personally think it's a mistake to ignore the tables, as the excercises provide good familiarity with an important segment of data if the instructor approaches it correctly.

 

[Kingpatzer]

However, I personally think it's a mistake to ignore the tables, as the excercises provide good familiarity with an important segment of data if the instructor approaches it correctly.

I appreciate this opinion, and I honestly shared it when this change first started. But after I spent some time thinking about it, and in the classroom without a table in sight, I definitely changed my mind.

Part of that change was driven from my own experience. When I was first learning higher level mathematics, we used tables to work out nearly everything. Geometric function tables, logarithmic tables, and so on. The last 20-50 pages of most every math text was an appendix of tables. When calculators that could do more than the 4 basic arithmetic functions started showing up they at first were banned from the classroom -- because using the tables supposedly gave the student insight into what is going on. And it was always possible that we'd hit the wrong button so we should have practice on the tables so we could double check our results, and so on. In other words, all of the arguments that are currently happening in this forum on tables versus computers.

Today, modern math textbooks don't even include the table appendixes.

There's no magic about tables that provides enlightenment. There is magic about quality instruction from a knowledgeable, conscientious and caring instructor; but there is nothing special about tables.

 

[Quero]

I guess because the instructors I've had did a lot more than "tracing your finger along a line". I agree that if that is all the instructor is doing, then you're not learning what you need to know as a diver. As for teaching the student his computer, I'm assuming they are learning the computer available from their training facility, with the rare student possibly purchasing one before training. What happens when they actually purchase their own computer, and its operation is quite different? I have two computers from the same manufacturer, and while their algorithms are identical, their operation isn't even close.

One of the things that happened in my classes, is that working the tables was drilled so thoroughly that the NDL's almost became second nature. While the square profiles taught with tables do not correspond with the multi-level profiles allowed by computers, knowing the information behind the algorithms can allow for better decisions underwater. I agree that computers should be stressed much more than they are, and I'm guess'timating that will happen soon...curriculum changes tend to lag behind market saturation in any given industry. However, I personally think it's a mistake to ignore the tables, as the excercises provide good familiarity with an important segment of data if the instructor approaches it correctly.

I understand your point, and I don't think we are saying different things, but simply coming from different perspectives about how to illustrate the theory. If discussion of compression, saturation, decompression, desaturation, algorithms, etc., is given proper emphasis, it can just as easily be illustrated by data from a computer display as it can be by data from a table. Those two types of tools are nothing more than ways to display the results of the calculations. Therefore, it's equally possible to cover the "why's" by teaching computer-based dive planning or by teaching table-based dive planning.

You ask what happens when a student is presented with a different dive computer from the one s/he used in the computer-based dive planning segment of the course. To me that's a red herring. It's like saying that when you learn to drive, you will only be able to operate the same sort of car you used in your driver's ed class. In actual practice, people learn to expect every car to have similar sorts of controls and when we get behind the wheel of a rental, for example, we just take a few moments to identify how to activate each of the different features we are going need. The same holds true for dive computers. Students who have received instruction in how to plan dives using a computer will have certain expectations of what kinds of information they can get from it and the sorts of planning they are able to perform by using it. They all do pretty similar things after all; it's only the process of activating the functions that changes significantly. This is where the cheat sheet flow chart thing comes into play. I include one of these in the storage box for every rental computer I have available. It's the divers' responsibility to take a few moments to review the process of accessing the functions in order to use the computers appropriately in planning and monitoring their dives.

What I personally think is the big mistake is a failure to adequately emphasize dive planning during early dive training. Most divers I see on boats are neither planning dives using tables nor planning dives using computer displays. This is what I think we need to be concerned about rather than railing against the possibility of retiring flat tables (which, BTW, I still teach). Maybe we need a new thread to discuss and share the different means and methods we use for a) teaching decompression theory and b) creating the dive planning habit in our Open Water students regardless of which data display method we employ. I would be very interested in hearing what my colleagues here do and in picking up new ideas from the wealth of experience represented. I actually asked one poster in this thread to outline what he does when he teaches theory, but he simply blew me off up in post #921.

 

[illinoisdiver]

I just finished my OW class in IL. Our instructor has been teaching for about 20 years and diving about 40. Our class was the first class where they did not teach tables at all and taught the computers. It was easy to follow and understand the concept of what they are telling you. The computers are part of the equipment provided in class for the dives. He believes this is long overdue. Part of his theory, speaking for him, is that you are no longer strapped to sticking to the plan on a table. If you don't follow your plan off the table, you will not have a accurate reading for allowable nitrogen. With the computer, if you go off of the planned dive depth and times, it will calculate this for you. Adding much more freedom to your dive. They way he describes it, most dive shops if they are trying to be up to date and especially for tourism dive sites will have computers to rent, cheap also.
This is the way of the future for new divers. The information is the same on a computer and a dive table. The computer just saves you the hassle and does the work for you. He has given me examples when they go on a dive, say in Bonaire, they seperate the groups with tables from the computers after the briefing. The computer divers go diving and the table divers sit on the boat and figure out there dive times and depths and then go diving.

 

[Eric Sedletzky]

What's eventually going to happen is tables will just be a historical footnote in diving and computers will be the norm (it sounds like it's already happened).
Tables will be just for vintage diving buffs along with double hose regs, oval masks and the like.

Why teach children to do basic arithmatic long hand when pocket calculators are so cheap now.
Learning to do math the old way is silly when it's so much easier and quicker just to use a calculator.
Figuring out how to work a problem on paper is a waste of time, and not very green I might add.
Addition, subtraction, multiplication, division, there are computers to do all this for us now.

 

[Jim Lapenta]

What's eventually going to happen is tables will just be a historical footnote in diving and computers will be the norm (it sounds like it's already happened).
Tables will be just for vintage diving buffs along with double hose regs, oval masks and the like.

Why teach children to do basic arithmatic long hand when pocket calculators are so cheap now.
Learning to do math the old way is silly when it's so much easier and quicker just to use a calculator.
Figuring out how to work a problem on paper is a waste of time, and not very green I might add.
Addition, subtraction, multiplication, division, there are computers to do all this for us now.

I agree. No need to have a kid working at McDonalds who can make change if the register goes down. Better for them to look baffled when I hand them 10.13 instead of a ten after they have already opened the cash drawer. I want to have to tell them how muich change I should get. My retirement is coming in a few years and they can contribute to that with their ignorance of basic math.

I don;t disagree with teaching computer only if that is what the student and instructor agree upon. If the student tells me they are going to buy a comp right away, which I try to discourage in favor of using square profiles and tables for the first few dives after certification, they are welcome to. I will go over the operation of their computer with them at no charge provided I know what it is. My objection is based on my own experience and it goes back to Quero's comment on the lack of real training and experience in training with dive planning.

My own Ow class focused on how to be back on the boat with 500 psi using the rule of thirds. And that was it. No real discussion on planning that using my SAC rate, how to determine it, etc. I get students involved in dive planning from the first pool session when we start doing weight checks and I make them responsible for that and recording that info. I have them plan the swim portions of the sessions by allowing them to decide what skills they want to work on during those. In class it's highly stressed that when they get out of the class and have their cards that they not trust anyone but themselves to plan their dives. And that if they do go on guided dives and the guide at any time suggests they do something or go somewhere that is against their recommended limits or experience level that they are under no obligation to follow that plan. Better to call the dive.

When we go over tables and discuss their usage we look at the reality of square profiles and that they are not what really happens. But if I take actual profiles from some of my earlier computer dives and drop them into the confines of those profiles they see the built in safety margins that using square profiles offers. Many of the local areas and the students I have taught so far plan on doing sites with hard bottoms or where the actual dive times are dictated by the boat operators. For OW divers planning dives on tables is a good exercise in this.

My own experience with a computer for the first time was something I see as typical for many new divers. Armed with the knowledge that the comp takes samples say every 30 seconds and therefore gives a fairly accurate profile coupled with lack of guidance in good judgment divers will fly the computers right up into the zone just before the red thinking that is safe. Hell I did! Why not? It's a computer, it's more accurate, it reads the depth every 30 seconds, it knows where my nitrogen is at all times, good to go right? Well what if it doesn't know that I have a medical condition that may affect my ability to off gas, or that I am not some superfit 25 yr old. What if the algorithm is not based on my body type, fitness level, how hydrated I usually am?

No, the problem I have with computers only is not them, it is that none of the other stuff is adequately addressed to make using them truly safe. Good judgment, common sense, using them as back up for the brain, USING THE BRAIN period! If it were stressed that the computer is only a tool, that it does not by itself keep you safe, that DM's and Guides are not to be trusted unless specifically hired for you alone- and even then it does not relieve the diver of any responsibility for themself- when it comes to planning, then I'd have no issue at all. But I find that when I have divers do tables and use the pwoer points from our presentation to illustrate the relationship between time, depth, and the process of on-gassing and off-gassing where they see the amount of molecules of O2 and N2 being absorbed they get it. They realize that when I illustrate the idea of a rapid ascent using Henry's law and Boyle's law why dive planning and tracking nitrogen uptake is so important.

It only takes a little time and belief in the intelligence of the student. I don't train underwater tourists. Don't want to. Students are not dumb. I have a 12 yr old student that understands the whole concept. Knows about tissue differences-slow vs fast, understands the importance of slow ascents and not doing them only because the instructor said she should. Knows about actual vs theoretical profiles. And sees the wisdom in keeping that in mind, especially as a new diver who should not be going near the NDL's anyway. I'd ramble on more but have to leave to teach a rescue class.

 

[FritzCat66]

The fact is, you should be able to "fly" a computer right up to the limits it displays. The only reason you can't is because the algorithms and theories behind nitrogen absorption, offgassing, and other physiological effects of breathing gas under pressure are still often inaccurate, teh physiology and physics poorly understood, and the models reflect that poor understanding.

This poor understanding of what's actually going on physiologically affects both table calculations and computer algorithms.

If the models ever become more refined, or (even better, IMHO) if we figure out some technology that reliably renders some concrete empirical physiological measurement of actual tissue gas levels instead of the estimates from an arbitrary mathematical model, then all these discussions will be moot, because that computer could be dead-on accurate.

Until then, however, it seems to me that it would be best to emphasize to all students, whether teaching tables or computers, that these theoretical models are all quite imperfect, and the imperfections add up when doing multiple dives over short periods of time with varying profiles, various levels of work, differing gasses, and even across different divers of varying ages, among other factors known and as yet unknown.

 

[lamont]

Actually, you shouldn't necessarily be able to do that.

Most deco theory was developed on square profiles. You went down, did your work and came straight back up with no sight seeing that wasn't required.

Using the same algorithms to do multi-level diving or 'riding-the-curve' is not what they were designed or tested for.

And I don't believe there has been much (or any?) research on validating that the algorithms are as effective in predicting DCS risk when doing multilevel diving. Basically the recreational diving population is doing a large lab experiment on the validity of using the models in this fashion.

Of course most computer manufacturers include additional conservatism because if they're at all smart, they know this and don't want to get sued by divers who 'ride the curve' and wind up bent.

The fact is, you should be able to "fly" a computer right up to the limits it displays. The only reason you can't is because the algorithms and theories behind nitrogen absorption, offgassing, and other physiological effects of breathing gas under pressure are still often inaccurate, teh physiology and physics poorly understood, and the models reflect that poor understanding.

This poor understanding of what's actually going on physiologically affects both table calculations and computer algorithms.

If the models ever become more refined, or (even better, IMHO) if we figure out some technology that reliably renders some concrete empirical physiological measurement of actual tissue gas levels instead of the estimates from an arbitrary mathematical model, then all these discussions will be moot, because that computer could be dead-on accurate.

Until then, however, it seems to me that it would be best to emphasize to all students, whether teaching tables or computers, that these theoretical models are all quite imperfect, and the imperfections add up when doing multiple dives over short periods of time with varying profiles, various levels of work, differing gasses, and even across different divers of varying ages, among other factors known and as yet unknown.

 

[John_B]

The fact is, you should be able to "fly" a computer right up to the limits it displays. The only reason you can't is because the algorithms and theories behind nitrogen absorption, offgassing, and other physiological effects of breathing gas under pressure are still often inaccurate, teh physiology and physics poorly understood, and the models reflect that poor understanding.

This poor understanding of what's actually going on physiologically affects both table calculations and computer algorithms.

If the models ever become more refined, or (even better, IMHO) if we figure out some technology that reliably renders some concrete empirical physiological measurement of actual tissue gas levels instead of the estimates from an arbitrary mathematical model, then all these discussions will be moot, because that computer could be dead-on accurate.

Estimates with mathematical models? This stuff was developed by bending goats!. So why wouldn't you want to teach new divers to turn their brains off and fly the NDL?

 

[FritzCat66]

Estimates with mathematical models? This stuff was developed by bending goats!

Actually, you shouldn't necessarily be able to do that.

Using the same algorithms to do multi-level diving or 'riding-the-curve' is not what they were designed or tested for.

And I don't believe there has been much (or any?) research on validating that the algorithms are as effective in predicting DCS risk when doing multilevel diving. Basically the recreational diving population is doing a large lab experiment on the validity of using the models in this fashion.

Yeah, that would be part of what I was referring to with the whole "the algorithms and theories behind nitrogen absorption, offgassing, and other physiological effects of breathing gas under pressure are still often inaccurate, the physiology and physics poorly understood, and the models reflect that poor understanding" thing.

Tables and computers are based on mathematical models which are in turn based on statistical evidence from research measuring tissue absorption and offgassing in extremely indirect ways. Including, yes, goats and pigs. Furthermore, as Lamont mentioned, most of the statistical data was developed using square profiles, a digital profile that doesn't much match the analog world.

But if we really knew under what precise circumstances a particular diver doing real-world multilevel dives would develop DCS with a high degree of accuracy, and if you could measure all the related parameters, and if you had a computer that could factor in all the realtime data and crunch out a genuine NDL number, then why wouldn't you be able to "ride" that number? Aside from reserving some amount for contingency, you wouldn't need to worry about it.

But right now that's all some sci-fi future; we have to deal with the imprecision of what we have now, goats and pigs and bent Navy recruits and all.