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January 17, 2008

The Dive Computer Blues

January is never a great time for divers unless, of course, you're lucky enough to have booked a dive trip to some sunny paradise, like I promised myself I'd do, but never got around to it. So it's cold outside and the last dive seems ever farther away and you don't know when you get to dive again. That's when you spend time reading dive magazines, go to scuba sites, or catch up on reading dive books. This morning I perused the latest issue of Alert Diver, the bimonhtly publication by DAN, the Divers Avert Network. It's a 64-page saddle-stitched production that makes up in good content what it lacks in commercial design and polish. I like reading it and learn something new every time.

What caught my eye this morning was an article entitled "Deep Calculations, Deep Trouble -- Exploring Safety in Dive Computers." This is a topic I am greatly interested in. I love computers in every shape or form and cannot imagine life without them. But dive computers are somehow different, and I don't feel anywhere near as at home with them as I do with any other computer, and that goes for the ones under the hood of cars and such. I trust my dive computer, and like everyone else, I think dive computers undoubtedly revolutionized diving and made it safer and more convenient. But there are dark sides.

The DAN article, written by Rick Layton, reported on the results of a recent Scuba STAR Network safety survey that investigated how scuba divers use their dive computers, what they know about them, and what experiences they've had with them. The survey didn't have a huge sample, just 42 divers, and may or may not be statistically significant. However, the results are pretty much what I expected, and they are alarming.

The survey said that only 10% of the divers actually learned to use their dive computer with an instructor or in a class. The vast majority simply used the manual that came with the computer, if anything at all. A oood half felt that the training materials were lacking and too complicated or disorganized. The survey also showed that divers are unhappy about the almost total lack of dive computer training in formal scuba classes. They suggested at least a review of all the common features, advantages, disadvantages and problems associated with different types of computers.

An appalling 60% of the respondents reported problems with their dive computer. Many felt screens were unreadable. Others reported blank screens, erroneous data, frozen computers, loss of some functionality, battery problems, and so on. Some computer failed to register depth, failed to display desaturation time, reset themselves, stopped displaying remaining air, or had inadequate rapid ascent warnings. As a result, almost 2/3rd of the respondents said they take along dive tables, and almost a third carries a spare computer.

That is certainly no vote of confidence. And I could definitely relate. Although my own dive computer has worked flawlessly for the year and a half that I have had it, I consider it far from perfect. Its user interface is virtually impossible to figure out. So much so that I have essentially given up trying to understand all the many features it has. I gave the manual several serious tries, but it is so poorly written and organized that I simply cannot figure it out and always give up in frustration. Too bad that there is not a large enough market to warrant a separate "Idiot" book for dive computers. That I understand. But why the manufacturer of my dive computer cannot have a tech writer overhaul their atrocious manual is beyond me. I mean, it could save lives.

The same issue of Alert Diver had another article on dive computers. It was entitled "Living with Dive Computers" and written by Dr. Neal W. Pollock. Dr. Pollock, a research physiologist at the Center for Hyperbaric Medicine and Environmental Physiology at the Duke University Medical Center, listed the various advantages of a dive computer, but also the many things it cannot do, or cannot do yet. However, he starts out saying, "You should know not only which buttons to push to make your computer work, but which mathematical model or model derivation it employs for decompression computation."

I agree, of course, that divers should know which buttons to push, and it's really, really sad that I, who consider myself somewhat of a computer expert, do not know which buttons to push to properly use my dive computer. Heck, I can barely see half the tiny little numbers and symbols on its tiny little low-contrast LCD. But now I am even supposed to know which mathematical model it employs for decompression calculations and, presumably, what that means to me?? Though I have a doctoral degree myself, and in a technical discipline, I don't think that expectation is remotely realistic. And if it isn't for someone like me who always wants to know how things work, I think there are others who may struggle with the concept.

But let's say it'd indeed be prudent to a) learn what buttons to push, and b) know the mathematical models that are used in dive computers. What would that mean? I'd say even the former is nearly impossible. Virtually every dive computer is different. I've seen more than one Scuba instructor unable to explain the operation of a student's Dive computer, and those were good instructors. Dive computers do not have a common interface, like Microsoft Windows or the Mac OS, or eve common controls, like computers have a mouse or a touchpad. So instructors may begin spending as much on dive computer basics as they do on dive tables.

Then they may have to get into the difference between table-based computers and model-based computers. Table-based is simple; the computer just uses the dive tables and quickly calculates all you need to know. But most dive computers are model-based, i.e. they make all sorts of assumptions. The oldest and most traditional model uses the Haldane models, named after the Scottish scientist who developed the theories and tables for the British Royal Navy. Haldane tables and concepts still form the basis for most die tables and dive computers, but there are many others as well.

What this means is that a diver would have to know not only about the Haldane theories, but also about statistical models, variable permeability models, reduced gradiant bubble models, slab models, Series models, and EL (exponential/linear) models. Add to that the various proprietary models, hybrids and assorted secret sauces manufacturers use in their computers, and the likelihood that many divers know what mathematical model their dive computer uses and what that entails is essentially nil.

Can we hope for standardization? Probably not. Will there be ongoing research that in conjunction with advancing technology will result in ever more sophisticated dive computers? Definitely.

Posted by conradb212 at January 17, 2008 10:47 PM

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