Average depth calculation

[wedivebc]

Playing devil's advocate....if the results are the same what possible advantage does this technique have over the use of the computer? The computer will give you the same results every single time for a million dives..... With doing the math manually you only introduce the possibility (In fact I would say *certainty*) of human error.

R..

Need to clarify computer. There is the dive computer that is shunned by ratio deco proponents and the desktop computer which is where the pre-dive planning takes place.

 

[JeffG]

Playing devil's advocate....if the results are the same what possible advantage does this technique have over the use of the computer? The computer will give you the same results every single time for a million dives..... With doing the math manually you only introduce the possibility (In fact I would say *certainty*) of human error.

R..

One is proactive the other is reactive. One can only use 1 algorithm, the other can use any algorithm.

 

[Spectre]

Playing devil's advocate....if the results are the same what possible advantage does this technique have over the use of the computer? The computer will give you the same results every single time for a million dives..... With doing the math manually you only introduce the possibility (In fact I would say *certainty*) of human error.

I don't really want to get into a 'computer vs. tables' debate, but I'll just give a couple quick things on that. I used to dive my Stinger in computer mode as backup; when I cleared 'my' deco, I verified the computer was clear. It was a fine method at the time. One day I had about 12 minutes of deco. After 30 minutes when I had 8 minutes of deco left, my buddy was starting to get really pissed. When she said goodbye was when I decided 'screw it', bent the hell out of my computer, tied it to a spool and tossed it overboard to clear enough so I could convert it to gauge mode.

I've not used a computer since.

I have a method that has worked just fine for well over 150 dives, why would I want to go drop huge sums of money on a tool that not only does something I can already do, but run the risk of trying to get me to do something I don't agree with? I always have continency plans and will fall back to them if I have any lack of confidence in my calculations; and since I'm either comparing my calculations with a buddy on a computer, or a buddy doing their own calcs, any sort of mathematical errors found quite quickly.

For the record; like pony bottles, helmets and spg's on both posts, I won't ever tell you what you should do, only what I do and why I do it, and perhaps a few things to think about during your diving career; and let you decide for yourself. I think I stated at the beginning of this thread that not many people would need a computer that calculates average depth. A bottom timer, yea it might be nice for a backup situation, but I would be afraid that too many people would depend on that and stop paying attention to their profile.

 

[Diver0001]

Need to clarify computer. There is the dive computer that is shunned by ratio deco proponents and the desktop computer which is where the pre-dive planning takes place.

A computer intelligently used will render the same results and is perfectly compatible with ratio deco but without the potential for human error. Ratio deco is a set of rules for governing your ascent/ascent rate..... they can be applied with any model you choose to use.

Just as Jeff points out.

R..

 

[Diver0001]

I don't really want to get into a 'computer vs. tables' debate, but I'll just give a couple quick things on that. I used to dive my Stinger in computer mode as backup; when I cleared 'my' deco, I verified the computer was clear. It was a fine method at the time. One day I had about 12 minutes of deco. After 30 minutes when I had 8 minutes of deco left, my buddy was starting to get really pissed. When she said goodbye was when I decided 'screw it', bent the hell out of my computer, tied it to a spool and tossed it overboard to clear enough so I could convert it to gauge mode.

Then it's concievable that you weren't doing adequate deco, wouldn't you say? There are no short cuts. There is adequate deco or not. Extreme divers are proving over and over that modern models like your stinger don't give adequate deco. Doing less than that only increases your risk. I think that we need to consider what extreme divers are doing and project that on to shallow dives, as I said previously because the evidence is conlusive that none of the techniques are really good. And if the stinger is already marginal then doing less than that should give you serious alarm bells.

Don't you think?

R..

 

[Spectre]

Then it's concievable that you weren't doing adequate deco, wouldn't you say? There are no short cuts. There is adequate deco or not. Extreme divers are proving over and over that modern models like your stinger don't give adequate deco. Doing less than that only increases your risk. I think that we need to consider what extreme divers are doing and project that on to shallow dives, as I said previously because the evidence is conlusive that none of the techniques are really good. And if the stinger is already marginal then doing less than that should give you serious alarm bells.

Let's just run some numbers on the dive in question. Ascent began after 33 minutes, a max depth of 124 feet, an average depth of 97 on 32% [I think, I don't recall, it could have been 30%]. Even assuming my ascent was too slow, and going with the time to 40 ft; that's 42 minutes at an average of 90 feet. let's call it 42 minutes at 120; or 16 minutes of deco. 20 minutes later I had 8 minutes left.

It doesn't take a rocket scientist to realize the ascent profiles I agree with don't agree with the stinger model. I much rather dive an ascent profile that I agree with, and be able to adjust my calculations based on the theory advancements rather than trust a computer where I don't even know what algorithm it is, let alone what generation of the algorithm. Not to mention that the buddy getting pissed off -is- one of those extreme divers that has used her body more than once to test the validity of deco theories.

Understand that I don't just blindly make up numbers. In fact I dive in more conservative then the numbers I generate. As I get more familiar with a location, it's profile; or as I get more experience in a deeper depth range, I adjust my conservatism based on my personal results. Not to mention that a computer doesn't know my personal state... how much sleep I had, how much water I had to drink, when the last time I got drunk was; the exertion level of the dive, etc etc etc...

I can pad my schedule based on my working knowledge of the theory, since I know what effect longer bottom time would do to my deco profile, what shorter bottom time would do, what more deco deeper would do to the overall picture. I can make those adjustments.... some algorithms will penalize me for it.

So, in a nutshell, no; there were no alarm bells, and no, I don't think there should have been. But like I said time and time and time again... buy your computer, dive your computer. If at some point you decide for yourself that you don't agree with it and want to know how those that also don't agree with it do their own modelling, then, and only then, read what I have to say.

 

[Diver0001]

Jeff,

I'm not trying to get you to defend your numbers, I'm just suggesting that we should take a much more serious look at what deep divers are doing and try to apply that thinking to shallow dives. Maybe the technique you use can create adequate deco for shallow dives in some circumstances but the people reading this thread are a community of cyber divers who only understand their computer superficially for the most part. I know you're not suggesting that anyone use your technique but I'm trying to point out that the more extreme the dive, the more skeptical you need to be about the approach. Extreme divers would label the approach as "madness". They would also label following the stinger as madness but at least it's madness that doesn't involve human error or getting other people to check your math.

It's funny that this thread comes up now, actually. I spent an hour talking about this very point with Mark Ellyatt last weekend. I think if he were responding on this thread, he would point out the the whole concept of conservative vs liberal is complete nonsense. In fact, I know for sure he would say that. Either you're using a model that gives you adequate deco or you're not.

If you're into it, try running decochek on some of your profiles after the fact. I'm open to the possibility that you're doing something that's giving you adequate deco but I'd like more confirmation than knowing that you haven't been bent yet.

I'm suggesting it because I've been using decochek to check my dives and it's been giving me 5-8 minutes of extra deco on the last stop. That's interesting because it's the same "error" you were talking about your stinger giving. Maybe your stinger wasn't malfunctioning at all.....

Just a thought.

R..

 

[Spectre]

They would also label following the stinger as madness but at least it's madness that doesn't involve human error or getting other people to check your math.

Understand I'm not talking about ratio deco. I'm talking about diving generated tables with only my bottom time 'adjusted' on the fly rather than going off the max depth of the dive.

And remember, all software can have bugs... just look at that computer that was recalled a few years ago because it was calculating your surface interval on your nitrox mix, rather than air.

 

[Diver0001]

Understand I'm not talking about ratio deco. I'm talking about diving generated tables with only my bottom time 'adjusted' on the fly rather than going off the max depth of the dive.

It's good that you pointed that out. A lot of these discussions seem to throw it all into the same witch's brew....

And remember, all software can have bugs... just look at that computer that was recalled a few years ago because it was calculating your surface interval on your nitrox mix, rather than air.

That's true. There can always be bugs. There can also be human error. As far as I know, there has been one serious computer bug (the Uwatec). The *models* might not always be terrific but they do tend to be pretty good at crunching the numbers...I'd personally put my money on a computer to average a long list of numbers better than I can do it.....

R..

 

[Spectre]

I'd personally put my money on a computer to average a long list of numbers better than I can do it.....

But you're not averaging a long list of numbers, you're just adding a fraction of a number to another number, and you really only need to be precise to within 5 feet. But then again, I'm a freak and I'll calculate partial pressure blending in my head when I'm bored on a long drive...

Plan your dive, dive your plan, and while your at it, try and keep track of your average depth. Compare what you think it was to what it comes out to be when you download your dive profile. If you find that you never end up with an average depth that is shallower then the actual average depth, you may decide the information is useable.