Is a computer actually necessary?

[IndigoBlue]

Uncle Pug once bubbled...

:shiver:

Actually if you get use to checking your gas supply and your depth every 5 minutes you might find that you activate your built in timer and develop not only a sense of timing but automatic tracking of your gas consumption as well.

I can tell time with my SPG.

It looks like "shiver's" post got pulled. That is too funny!

UncleP demonstrates how learning curve in an extremely experienced diver works. I completely agree with UncleP. More and more, my SPG and my depth gauge are my primary navigation devices. In addition, when vis is poor, the compass as well.

NDL dive times for dives shallower than 80 ft are more than generous enough to accomodate any 80 cu ft tank for any dive, air or nitrox. So as long as a diver pays attention to the SPG, and reverses course by the midpoint of the dive, you should get a nice inverted pyramid profile for both the outbound and inbound legs of the dive plan. NDL dive times for 90 and 100 ft are close to tank capacity for an 80, but with an adequate reserve, even then your SPG would tell you to turn around long before you reached the time limit, on air or nitrox. 100 ft is where I draw the line for rec diving, and 50 ft is where I draw the line for brand new divers.

After the first dive, when you are back on the boat or shore, then consulting the tables after factoring in your surface interval can be used to give you a new max depth, something in the range of 50 to 30 ft. The depth gauge then becomes the primary instrument, together with the SPG again.

Divers have been diving for decades without a computer, safely and successfully, with tables as their only resource.

I agree that with the advent of computers, diving has gotten easier for beginners who choose to utilize them. But beginners who chose to wait before buying a computer, or who choose not to buy a computer at all, have all the classic instrumentation options that have been around longer than computers have.

Either way, with or without a computer is fine. In my opinion.

A computer lets you be lazy. With a computer, you can ignor tables. And the computer will do all the surface interval and repetitive dive calculations for you as well. You can be really lazy with a computer.

Without a computer, you need to think. Unless you are a really experienced diver already,apparently like UncleP. Then almost everything about diving becomes reflexive anyway.

SPG, depth gauge, and compass. Those are the critical instruments. The computer is totally optional, in my opinion. But plan your dive, and dive your plan, and do not be lazy either! Then diving without a computer should work well for you, until you are ready to buy one, or until you make up your mind that you do not want one at all.

Of course the scuba store (SS ?) does not want you to believe the computer is optional. They want you to buy one. I did, eventually, but not right away.

 

[colorado_al]

I've been diving since 1989 and have been using a dive computer since 1997. I have had several brands, and setups. I think one of the most important things to remember, is always dive conservatively, on tables or on computer. That being said, I always check my plan on tables before the dive. I now use an air integrated wrist dive computer (UWATEC Aladin NitrOX) and one of the main advantages is one less hose. The computer has a sending unit that attaches to the regulator and sends via radio signals to the computer info on air pressure. I also enjoy downloading the data from my computer to my Palm Pilot, and using it for a digital dive log. When all is said and done however, the computer is just a toy that, for me, makes diving more fun, but not necessarily more safe. Computers and dive tables are all based on algorithms that may or may not work for you. I recommend using a computer, if you like that sort of thing, but above all, recommend diving a conservative profile on either tables or a computer. Your brain will thank you for it.

 

[Kendall Raine]

It's inspiring to see so many people who'd rather use their brain to monitor their deco situation than rely on a machine to do it for them. Certainly computers are a convenience, but blindly following them is a tempting and potentially dangerous thing to do. Anyone been following the lawsuit against Uwatec? You know, the one where the Aladdin Nitrox computer assumed you were breathing nitrox during the surface interval and calculating residual nitrogen that way. Several people who should know better got hit using that computer and now they're sueing.

Statistically, the proportion of "undeserved" hits is alarmingly high. I've seen statistics over 50%. If the models are right, how is this possible? The answer is the models are best guesses. To the extent they don't accurately model what's going on in your body, those errors compound across multiple dives. Following a computer to its limits reduces any inherent padding in the computer algorithm and this situations multiplies the more repetative dives you do. Now, anyone who argues that pushing the model is error by the diver not the computer has a point, but the computer itself is so seductive it leads the lazy down this path.

To me the most compelling of many reasons to leave your computer on your desk is situational awareness. With a little practice, the bandwidth it takes to mentally track your depth/time information is quite small. It's not zero, as with a computer, but why would you want to be so clueless about your deco status anyway? Now, it does compel you to actually plan and track your dives, but if that burden is too distracting, should you really be underwater in the first place?

 

[jviehe]

Kendall Raine once bubbled...

Statistically, the proportion of "undeserved" hits is alarmingly high. I've seen statistics over 50%. If the models are right, how is this possible? The answer is the models are best guesses. To the extent they don't accurately model what's going on in your body, those errors compound across multiple dives. Following a computer to its limits reduces any inherent padding in the computer algorithm and this situations multiplies the more repetative dives you do. Now, anyone who argues that pushing the model is error by the diver not the computer has a point, but the computer itself is so seductive it leads the lazy down this path.

Could you tell me where you got your "50% stat?" And is this referring to computers specifically or models in general?

 

[Kendall Raine]

I seem to recall the source was DAN, but I'm not sure whether the number was first or second hand-it was a while ago. I don't believe it was specific to computers, or algorithms, either. I've heard fractions larger than 50%, as well. Naturally, such statistics are squishy since the definition of "undeserved" means within NDL's as reported by the patient. Hence, it could contain bias. It also ignores the fact that the overall bends rate is really low. As such, whatever the number you use speaks to the wisdom of backing off model limits, particularly in repets, rather particular model efficacy. To give you an example, during the testing of the PADI RDP, researchers had one hit in roughly 1400 dives. That hit was within repetative parameters. The undeserved rate was therefore 100%, but you need to look behind the number to know what it means.

Now you've gone and piqued my curiosity. Maybe I'll call DAN and ask them what their latest number is.

 

[String]

Kendall Raine once bubbled...
It's inspiring to see so many people who'd rather use their brain to monitor their deco situation than rely on a machine to do it for them.

Well the brain is far less accurate in following the models. Why do people drive cars when they can walk? Why do calculators sell so well when an adding machine would do the job ?

Certainly computers are a convenience, but blindly following them is a tempting and potentially dangerous thing to do.

Dangerous yes. Tempting? Not for a well trained diver.

Anyone been following the lawsuit against Uwatec? You know, the one where the Aladdin Nitrox computer assumed you were breathing nitrox during the surface interval and calculating residual nitrogen that way. Several people who should know better got hit using that computer and now they're sueing.

So it was an error. Dont forget the PADI RDP wheel had a recall lately as well. This isnt an error specific to computers.

Statistically, the proportion of "undeserved" hits is alarmingly high. I've seen statistics over 50%. If the models are right, how is this possible? The answer is the models are best guesses. To the extent they don't accurately model what's going on in your body, those errors compound across multiple dives.

Yes everything is based on a statistical model. Computers can follow this statistical model more accurately than a brain can though.

Following a computer to its limits reduces any inherent padding in the computer algorithm and this situations multiplies the more repetative dives you do.

And likewise following the tables to the limit also reduces any inherent padding and increases the risk of a mishap.

Now, anyone who argues that pushing the model is error by the diver not the computer has a point, but the computer itself is so seductive it leads the lazy down this path.

Again, ive yet to see proof of this. Everyone here i know plans using tables as a worst case scenario and keeps a copy of tables in the BC pocket.

To me the most compelling of many reasons to leave your computer on your desk is situational awareness. With a little practice, the bandwidth it takes to mentally track your depth/time information is quite small.

However its far less accurate than using a computer to do the same task. Yes, the models are statistical guesses. A computer will follow the model accurately but your brain method is an inaccurate way of following an inaccurate model. Basically just adding another layer of uncertainty to it all.

It's not zero, as with a computer, but why would you want to be so clueless about your deco status anyway?

Who says people would be?

Now, it does compel you to actually plan and track your dives, but if that burden is too distracting, should you really be underwater in the first place? [/B]

If you are incapable of planning a dive you shouldnt be in the water computer or no computer. Training agencies all teach tables and dive planning so again your argument is just as true for tables as it is for computers.


Not one of your comments are specific to computers in diving and all can be just as accurately placed as an argument against tables ! Both follow a statistical model to reduce the chance of a decompression injury, neither are infallible and an untrained diver can hurt themselves either way with no real problem.

However i know my computer tracks my N2 loading far more accurately than the tables can possibly hope to and therefore i know its adhering to the model better. I still plan a worst case scenario dive using my tables but my computer is a VERY useful tool for non-worst case scenario dives.

 

[Kendall Raine]

Further to the question of where I got 50%, I rumaged around and found the DAN source I remembered. It was actually a 1998 report done under a grant from DAN Europe, but I trust you'll forgive the imprecision.

On page 1625 you'll find "Overall, the "deserved-to-undeserved" DCS ratio in a population of divers lies ~50%."

Here is the link for those who want to stomp around in the weeds: www.daneurope.org/eng/jap98.pdf.

 

[String]

jviehe once bubbled...


Could you tell me where you got your "50% stat?" And is this referring to computers specifically or models in general?

No idea where he got that from but a UK published statistic was 2/3 of DCS incidents were "undeserved hits". HOWEVER these were undeserved hits in accordance with the US Navy and other tables and definately NOT singled out to computers.

 

[Kendall Raine]

I think you misunderstood my point. I have nothing against inanimate objects, dive computers included. The objection is the tendency by some, obviously not you or anyone with whom you're acquainted, to blindly follow the blinking lights. When you simply have a bottom timer and a depth gauge, I believe you're compelled to pay more attention, particularly if you're depth averaging. Paying attention, as I pointed out, is the core issue. If you're using a computer and paying attention as if you weren't, then yes, fine, you have both a brain and a machine working for you.

Let me suggest a test to gauge how much you depend on your computer to do your thinking and planning for you. Next time you're diving, bring both a timer/depth gauge and your computer. Half way through the dive, hand your computer off to your buddy and conduct the remaining part of the dive without the computer. For the test to mean anything, you'll need to be honest and plan the dive as per usual-as if you intended to keep the computer the whole time.

If you don't notice any difference, you obviously plan and conduct the dive without needing the computer to think for you and the computer is truly a redundant system. If it feels uncomfortable, perhaps you have been leaning on your computer more than you thought.

Please let me know. I'll take your word for it.

 

[fgray1]

If you like to use a computer use it if not don't
If you like to walk to the store, walk, if not take your car.
If you like to mow your grass with a push mower, do it ,if not use the riding mower. Get my point