Average Depth Diving?

[limeyx]

(Try this again...I hate my laptop)

You are confusing Avg Depth usage with a Dive Profile created by Ratio Deco.

The dive profile wasn't working for her. Has nothing to do with avg depth. Given that Ratio Deco creates similar profiles to most modern deco software, that would also mean she would be incompatible to the profiles generated by them.

So which would lead me to believe that she would be incompatible with whatever deco algorithm that was in her computer.


Charlie, we have been talking about mixed gas diving here.

Oh, the voice of reason In fact, she'd likely have been even worse off on "standard" profiles due to coming shallower much quicker.

 

[jonnythan]

When 1 person gets bent while staying within the tables, we do not change the tables, nor does that person have the chance to switch over to "more conservative tables." They, ideally, do slower ascents (especially at the end) and don't get as close to the NDL.

I thought that was worth pointing out.

 

[JeffG]

First off, I'd rather you not call me an idiot if you can possibly help it.
Second, how do you really think that tables are generated? Maybe not by exactly that method, but it's all experimentation and reducing the statistical chances of getting injured to a "small enough" number.

Second, go tell that to people who regularly save multiple hours of decompression by doing just that.

Maybe he will tells us the "real" solution to getting a little bit bent on a pretty standard profile.

Gee....making your stops a little bit more conservative by adding time doesn't seem like a big stretch to me.

 

[TSandM]

Well, I have to butt in to say that there is quite a bit more behind the tables than just experimentation and reducing DCS to an acceptable level. There actually IS mathematical modelling of compartment loading and unloading, and gradients and acceptable levels of saturation. Anybody who is curious can actually SEE what is going on by downloading decompression software -- some have some beautiful graphs that show you what the model says is happening at depth, and as you ascend.

Where the experimentation and "acceptable DCS" rates come in is in deciding the basic assumptions for the table or algorithm -- for example, what the M values for the various compartments are. Those things ARE tinkered with, and that's why tables or computer algorithms require validation before they are released into general use.

 

[JeffG]

Well, I have to butt in to say that there is quite a bit more behind the tables than just experimentation and reducing DCS to an acceptable level. There actually IS mathematical modelling of compartment loading and unloading, and gradients and acceptable levels of saturation. Anybody who is curious can actually SEE what is going on by downloading decompression software -- some have some beautiful graphs that show you what the model says is happening at depth, and as you ascend.

Where the experimentation and "acceptable DCS" rates come in is in deciding the basic assumptions for the table or algorithm -- for example, what the M values for the various compartments are. Those things ARE tinkered with, and that's why tables or computer algorithms require validation before they are released into general use.

Maybe you can tell me where these magic compartments are.

Where is the 60min compartment? Is it below the spleen? Next to the liver?

 

[TSandM]

Jeff, you're talking to the wrong person . . . I've written before about the dismay with which I learned that this modelling is a highly abstract and essentially completely theoretical model, as nitrogen loading, on- and offgassing of various tissues has not been directly measured (nor do I want to volunteer to have a mass spec probe placed in my brain . . . ). But there IS a model, and calculation which is done. I just felt limey's comments suggested that the tables were derived by diving a lot of people and seeing which profiles produced DCS and which didn't. There IS more structure to it than that.

 

[JeffG]

But there IS a model, and calculation which is done. I just felt limey's comments suggested that the tables were derived by diving a lot of people and seeing which profiles produced DCS and which didn't. There IS more structure to it than that.

I guess the point I was going to make that I know its just a model. There are a few models out there, and they do not all agree.

Many things that are known to contribute to DCS are not covered by the models. Hydration, Fat Slob Factor, What did I eat this morning factor, Water Temp, did I flood my suit factor.

But people will babble on about compartments....m-values, etc etc and yet poo-poo something like ratio deco even though the science they "believe" in is flawed as well. (and yet they still take it as gospel)

I find that quite funny.

 

[Charlie99]

But there IS a model, and calculation which is done. I just felt limey's comments suggested that the tables were derived by diving a lot of people and seeing which profiles produced DCS and which didn't. There IS more structure to it than that.

And just as the model is developed and then tables that conform to that model are generated, one can also use those same models to validate other potential depth and time tracking methods, such as average depth tracking.

If you have reasonable faith in the model, then the first round of validation of a proposed deco tracking method is to run various profiles through it, and also through an underlying decompression model in which you already have reasonble faith because of prior experiments.

Put in simpler words, one can easily check the validity and the limits of validity of things like "average depth tracking" by cranking it through Decoplanner, GAP, VPM or other decompression programs.

 

[jonnythan]

Put in simpler words, one can easily check the validity and the limits of validity of things like "average depth tracking" by cranking it through Decoplanner, GAP, VPM or other decompression programs.

Absolutely agreed, and I highly suggest that all of the detractors understand the method and go ahead and try exactly this.

It's exactly what I did and continue to do on a regular basis both before and after dives.

 

[TheRedHead]

But people will babble on about compartments....m-values, etc etc and yet poo-poo something like ratio deco even though the science they "believe" in is flawed as well. (and yet they still take it as gospel)

Do you really think people believe that these compartments exist in the physical world rather than being mental constructs?