Do I really need a computer?

[boomx5]

This is a really interesting comment. Tables and dive computers are all based on the same basic theoretical model. What I would be really interested in knowing is what exactly are the kinds of dives that you do for which a dive computer, or for that matter any algorythm out there, can not be used. And to take that to the next step, exactly how do you plan your profiles?

Just very curious as I can't think of any profile for which a computer can't be used. To include deep diving with trimix. Though in those cases, the research upon which all of the tables and profiles are based is scant.

Thanks,

Steve

I never said a computer won't do the job, it just won't do the job I need it to very well. To even come close, I would need to spend over $1,000.00 on a trimix computer to tell me how to decompress. However, the profile a dive computer would generate would not be the profile I would subject my body to and at times would be utterly rediculous for our dives at altitude. I'm not going into the way we plan our dives simply because it would take to long to do. I'm really not trying to be difficult or keep some "super secret knowledge" from you because that's not the case...I just don't have the time. If you have something that works for you, then I say use it, but that's just the way we do things.

 

[halocline]

This statement is inaccurate.

Care to explain, rather than just say the guy is wrong? Might be a little more helpful. Of course there are different tables and computers with different algorithms...I think sff was saying that in general, computer algorithms are based on theories from tables, hence if you can use a table for a dive, you can also use a computer.

I don't have a problem with your disagreement, just in the way it was delivered.

 

[jonnythan]

Sure I would!

The tables are based on experimental data, not a theoretical model.

 

[Charlie99]

Sure I would!

The tables are based on experimental data, not a theoretical model.

If you want to split hairs, the tables are based on the model (or more correctly, are in conformance with the model). Most models were based upon theory and then tested. When testing, or real world feedback, indicate a problem with a model, then it get modified. Examples of this are Buhlmann ZHL16 A, B and C versions, and the VPM vs VPM-B.

Once you have a model, then you can work on ways to make it accesible and usable. Tables are a very crude way of representing a model. For example, the pressure groups of both the PADI and the USN/NAUI/YMCA/SSI tables are based upon 1 and only 1 compartment of the underlying model.

 

[jonnythan]

Someone correct me if I'm wrong.

The US Navy tables are based on Navy experiences with divers as diving was being developed.

Other agencies' tables are based on this, perhaps with the added benefit of doppler bubbling experiments on people.

If I'm wrong about the tables being based on actual experimental data rather than a theoretical model, I'd love to hear about it.

 

[PerroneFord]

Johnnythan, I think NAUI Tech is basing off VPM, and from what I hear, they teach VPlanner to run their profiles. I'd assume VPM-B version now.

I've only ever looked at IANTD NDL tables (and PADI NDL tables but don't tell anyone) for comparison. Unless you are doing deco diving, you are going to get pretty close to the same stuff from most models/tables.

 

[CIBDiving]

Someone correct me if I'm wrong.

consider yourself corrected - as usual you're wrong.

 

[Web Monkey]

I can't wait for the answer to this one.

Terry

This is a really interesting comment. Tables and dive computers are all based on the same basic theoretical model. What I would be really interested in knowing is what exactly are the kinds of dives that you do for which a dive computer, or for that matter any algorythm out there, can not be used. And to take that to the next step, exactly how do you plan your profiles?

Just very curious as I can't think of any profile for which a computer can't be used. To include deep diving with trimix. Though in those cases, the research upon which all of the tables and profiles are based is scant.

Thanks,

Steve

 

[Goose75]

it depends on the objective and degree of sophistiction to achieve the objective.

Internal combustion engines obviously don't 'need' a computer to operate - but as things like gas mileage, environmental emissions, etc. all became larger issues, they were used to better achieve such objectives...(snip)

But neither version of transportation worked or will work well if the organic brain is disengaged from the nut behind the wheel...(snip)

Likewise, jet aircraft didn't require computer control - the German fighter / interceptor models used in WWII had no such controls - but survivability of things as simple as takeoff and especially landing have increased dramatically with computer assistance for control, whether for military or commercial use - but pilots still engage their brains, especially during those steps to my knowledge.

This is why I don't understand why there's a paradigm that use of a computer inherently implies the lack of functioning of the organic brain for this sport.

I agree an internal combustion engine doesn't inherently need a computer but I believe some newer models that use computers to control injection of fuel do.

Most subsonic jet aircraft do not require a computer to operate but it is so integrated that "dead stick" wouldn't be a welcome proposition either. No pwer, heavy and far from home. Some military models that fly over your homes are built to be aerodynamically unstable - no computer, no control of pitch, yaw and roll. You couldn't glide far with the stubby wings anyway.

I agree that having a computer shouldn't turn off the brain. I think you should know your tables and how to operate your computer. If it tells me I'm clear to go to 130ft on EAN 40, I know that I have input something wrong or it has a major malfunction. I usually carry a backup so my first thought would be to check it. Should I not be carrying it, there should be a buddy close at hand to check theirs. If all three disagree with my brain, I'm not thinking clearly and it's time to end the dive anyway. I treat my computer the same way a pilot treats his instruments. If the brain and the instruments are in conflict you must stop, think about the situation and determine which to trust. For pilots it is the decision between potential gauge failure and potential vertigo.

 

[DiveGolfSki]

consider yourself corrected - as usual you're wrong.

No need to be hostile. For those you'd like some information on how computers work, I've always thought this article gives an interesting explanation (albeit simplified):

http://www.scubadiving.com/gear/dive_computers/dive_computer_secrets_revealed/0/

For those who are interested in this subject, Florida State has a good curriculum on diving and has several papers on tables and deco. Here's one:

http://www.adp.fsu.edu/pennotesfall2003/Section19.pdf

As far as how the US Navy dive tables were created, in 1912 the Navy set up a program to test tables and staged decompression based on the work of Haldane. As we all know, Haldane developed his theories by experimenting with GOATS. I'm not sure how the Navy tested Haldane's tables but I'm pretty sure it wasn't with goats ...
in fact, here's a quote from one of Navy diving history pages:

Until 1912, US Navy divers rarely went below 60 fsw (feet of seawater). In that year, Chief Gunner George D. Stillson set up a program to test Haldane's diving tables and methods of stage decompression. A companion goal of the program was to develop improvements in Navy diving equipment. Throughout a three-year period, first diving in tanks ashore and then in open water in Long Island Sound from the USS Walke (Destroyer No.34), the Navy divers went progressively deeper, eventually reaching 274 fsw.

So, I guess, Jonnythan's statement that "The US Navy tables are based on Navy experiences with divers as diving was being developed." is correct.

It should also be pointed out that US Navy divers (even back in 1912) were in better physical condition than your average recreational divers.