Number of Dives vs. Dive Hours

[boulderjohn]

I agree with the earlier comments of the importance of diversity over either the number of dives or hours. I live in Colorado, where there is very little decent local diving. My real diving is on trips I choose to take to diving areas. I have been to many different dive locations, but for some reason I always feel compelled to go somewhere warm. I think I am a pretty good warm water diver as a consequence of those experiences. Put me in a dry suit in Puget Sound, and I will be looking around for help immediately.

 

[in_cavediver]

Quite frankly, the numbers don't mean much to me anyway. A diver with 60 dives in the last year should be more experienced than a diver with 200 over 20 years. The best gauge of experience, in rec diving at least, is to see someone in the water. All the talk and numbers are just so much yada yada yada.

You know, we could come up with a generalized equation to give a weighted number for a divers 'appropriateness' to a given dive. It wouldn't be that difficult to factor in water temp, training, total expierence and recent expierence. We could then take in the planned dive paremeters and scale it to a idealized value of 0-1. In the end, we could come up with another cool number like SAC and maybe even give it another official sounding acronym and generate tables and the like for divers to plan with.

(Or maybe I am too much of an engineer and I quantify to many things)

 

[ClayJar]

(Or maybe I am too much of an engineer and I quantify to many things)

Engineer, you say? Then I assume that somewhere along the line, surface-adjusted dive time entered your models, eh?

The one problem is that while 10 minutes at 4 ata should obviously count twice as much as 10 minutes at 2 ata, diving at altitude should count *more* than diving at sea level, so there is probably a lesser-order term for altitude above mean sea level, otherwise the function would be monotonically decreasing with absolute pressure, which wouldn't seem to accurately model experience with diving at altitude.

As most of my dives have been negligibly removed from mean sea level, I actually calculated my surface-adjusted dive time one weekend... it was an enlighteningly enjoyable monstrosity of a number, but I *did* do 12 dives.

(Did chemical engineering alter my brain, or was I this odd to begin with? The world may never know.)

 

[Walter]

Who cares? I think Tom covered it pretty well.

 

[Lightning Fish]

The one problem is that while 10 minutes at 4 ata should obviously count twice as much as 10 minutes at 2 ata, diving at altitude ...

So a 'casual', high vis, stress-free dive to 4 ata for 10 minutes is worth more experience than a low vis, high current, high swell dive to 2 ata for 10 minutes.



It all has to be taken in context.

Bill.

 

[mfalco]

Well lets start with knowing your dive time. If you are not diving with some sort of time piece you are on a slippery slope. It's true that a novice on a conservative shore dive will run out of air before the NDL is anywhere in sight but you should really be diving with some sort of watch, they are cheap.

Pete

The shore dive I do most often (1.5 miles from my house) goes down to 65' feet almost instantly. A novice probably will have the NDL in sight before they run out of air.

 

[ClayJar]

So a 'casual', high vis, stress-free dive to 4 ata for 10 minutes is worth more experience than a low vis, high current, high swell dive to 2 ata for 10 minutes.

Absolutely (when dealing with a first-order polynomial model).

Now, if you want to start adding higher-order terms, feel free, but I have a feeling that you're going to end up with a bunch of non-linear terms. I mean, hey, I wouldn't put it past you to go directly to NP, at which point, you'll probably be using iterative numeric solvers to come up with plausible solutions to the models. (It would make for a more visible edition of a "dive computer" to process it all, of course.)

Or, in other words, be careful when meddling with engineering humor (or replying to it as if it were canon). You get more-or-less exponentially increasing responses.

 

[in_cavediver]

(It would make for a more visible edition of a "dive computer" to process it all, of course.)

Ya know, you may be on to something here. Just think, ANOTHER must have item to sell divers so they always know their 'appropriateness' factor. Heck, we could even make it submersible and perhaps even make a correlation to injury rates to give a diver the real-time probablity of getting hurt! Call it the Darwin factor. (hey guys, I just jumped up to a 90% chance of getting a darwin award!)

And for the meat of the engineering model... Who assumed it would be linear! All good engineering things in life are some form of a natural log function. (Plus, for the DIR crowd, they could use more buttons on the calculator to do the math by hand)

 

[Tom Smedley]

Oh man! you opened your mouth and now Halcyon has to retool to manufacture black calculators with a seven foot wire.

(Plus, for the DIR crowd, they could use more buttons on the calculator to do the math by hand)

 

[Lightning Fish]

Absolutely (when dealing with a first-order polynomial model).

Now, if you want to start adding higher-order terms, feel free, but I have a feeling that you're going to end up with a bunch of non-linear terms. I mean, hey, I wouldn't put it past you to go directly to NP, at which point, you'll probably be using iterative numeric solvers to come up with plausible solutions to the models. (It would make for a more visible edition of a "dive computer" to process it all, of course.)

Or, in other words, be careful when meddling with engineering humor (or replying to it as if it were canon). You get more-or-less exponentially increasing responses.

A first order model? Dude, 6th order state-space model at least and non-linear. Then, of course, Jacobian linearization becomes necessary. Instead of an iterative solver I would recommend a Kalman filter updated with data readings (perhaps pulse rate or contraction of the corrugator muscle) from the diver.

Of course it would be canonical, until proven otherwise. Nice term, that, canonical. Always wondered about its origin, any idea where it comes from?

Bill.