The old tables vs computer argument

[gcbryan]

You should know the tables for the day that will come when your computer gives out that error message, Windows Subscription Expired. Garbage in and garbage out. Knowing the tables allows the computer diver to evaluate the validity of what his computer is telling him and to complete a dive safely when it fails. Oh, you carry two to cross check, ok, which one is right? Your brain is a computer, the best ever made.

N

What you should know is what's behind the tables and the computer. If you have to keep looking at the tables then you haven't learned those and that's not any better than having to keep staring at a computer.

It's a silly argument however for anyone to suggest that it's one or the other. Everyone should be able to read a computer, dive table, and a book for that matter.

 

[Mr Carcharodon]

So which is it? So complicated that everyone must take a class or simple enough that even a professional decompression schedule designer and researcher with a PhD could grasp without personal coaching?

I think it is rather simple. Certainly simpler that using tables which as been the standard since before my time. Diving as an industry seems to have a lot of classes about fairly trivial topics. The prevailing assumption seems to be a that significant fraction of potential users can screw up almost any topic, so we have classes. Clearly not everyone needs them. Of course the more formal instruction does let you know what others are doing and not what you imagine them to be doing which may not always be the same.

I would be all for a peer reviewed study as well. But I doubt anyone from GUE or UTD is going to pay for this since they have been diving this way for a for more than a decade and they are at a point where they can say from experience it works. Good results over a long period of time and many dives is a sort of validation.

 

[Blackwood]

Not close enough for me to understand you point.

Yes, in the light of day, it was exceptionally bad.

What I'm meaning is this:

If we accept Buhlmann and VPM as being tested (this post is not an assertion that they are), and if the obligations determined by ratio envelope those produced by the Buhlmann and VPM algorithms, are we not safe (if not scientifically correct) in treating those obligations as tested?

Here comes another potentially bad analogy, this time with respect to load cases and stress analysis. If I have one load case which is for 10gs lateral and 20gs longitudinal, and another load case which is for 6gs lateral and 15gs longitudinal, I (or rather my stress analyst) is not going to waste time running both cases. The first case envelopes the second.

(perhaps not so) Similarly, the setpoint and associated rules of ratio deco (are intended to) envelope the Buhlmann and VPM solutions.

If you have to do that what use is it, except perhaps as an emergency response to having to alter the plan on the fly?

Because I don't need to do it for dives which are within giggle room of other dives I've safely completed. I've convinced myself it is within spitting distance of "accepted algorithms" for dives in and around my current training and experience limitations. I'll similarly convince myself if and when I proceed much deeper or much longer.

 

[boulderjohn]

If we accept Buhlmann and VPM as being tested (this post is not an assertion that they are), and if the obligations determined by ratio envelope those produced by the Buhlmann and VPM algorithms, are we not safe (if not scientifically correct) in treating those obligations as tested?

Here comes another potentially bad analogy, this time with respect to load cases and stress analysis. If I have one load case which is for 10gs lateral and 20gs longitudinal, and another load case which is for 6gs lateral and 15gs longitudinal, I (or rather my stress analyst) is not going to waste time running both cases. The first case envelopes the second.

(perhaps not so) Similarly, the setpoint and associated rules of ratio deco (are intended to) envelope the Buhlmann and VPM solutions.

But it is not true.

When you read (or listen to) the theory behind RD, it specifically says that Buholmann was wrong and should not be followed. Herb Ross, developer of the VPM-based V-Planner, says RD and V-Planner are not consistent with one another.

Andrew Georgitsis told me directly and in so many words that these software programs are wrong.

As for finding comfort in the fact that these other programs have been tested and so RD has been tested, as I said earlier, VPM-based programs have not really been tested, either.

 

[Blackwood]

John - I don't disagree.