I thought for a long time in this discussion that people were simply moving goal posts. Now I see that they have not even agreed on what the dame is.
I thought the statement that you can use average depth with tables and get effectively the same answer was what was being said, and that such a practice was widespread.
Now you are saying that your point is you get a safe answer, but not the same answer. OK.
But then the other players are not even using average depth of the dive, but rather average depth of the bottom (or the deep segment of the dive) as far as I can tell. Totally different game. Then others are arguing about 4h dives or trimix or saturation or something. Different game, not even the same playing field. And some say well that's what we do locally, which is hardly "widespread."
It certainly appears that the DIR/GUE/UTD guys doing heavy deco have figured out a way to do some sort of (to me arbitrary) averaging that allows them to mostly stay away from DCS. Great.
But folks using the usual tables, from the mainstream agencies, really ought to avoid this "average depth" nonsense. It demonstrably does not work to give the same answer as their max depth and the tables. yes, it may provide a safe answer, although that has not really been shown...just some example where it does work. It would be even safer on a multilevel dive to just use the max depth -- as the tables intended -- and accept that the dive will be shorter than desirable. Or use a multi-level diving tool. Or use a damn computer.
I'm not sure Tursiops, what your goal here is. To warn recreational divers not to use average depth when planning a dive using tables? For sure... but this is a given. They have no knowledge of decompression theory and are using computers in any case. So what is really the discussion? The inital question was on what GF are used. That's in itself not a recreational question, so excuse me for replying to this question explaining how i plan technical dives.
Will I use max depth as my planning depth when doing a recreational dive... yes I probably will, because it's easier (no calculation) and adds a bit of conservativism to the dive... or I just switch the gauge to computer and dive a computer and switch my brain off
But the initial discussion was on GF, and that's in itself not a recreational discussion, and I just said how I plan technical dives.
- We are not moving goal posts. Calculating avg depth and using it in your dive planning (even on the fly during the dive) is part of the standard GUE procedures and is taught in the curriculum. If you want to look it up I'm sure you'll be able to find the GUE procedures.
- Calculating/using the average depth of the bottom part of your dive (non ascend) is a perfectly feasible way of planning a dive and in reality because the variance between min (bottom) depth and max (bottom depth) is reasonably small. You might say this is anekdotal and not supported by science, but I have done 100s of trimix dives doing this like others and it just works.
- Doing deep and long dives with extended deco (2 hours plus) is in any case only marginally supported by theoretical models. When the switch between different models or adjustment of GF can mean the difference of hours less or more deco, it becomes all very grey in any case and people/teams make individual decisions.
So unless you come up with some hard data that using average depth in the bottom part of technical dives is less optimal I won't change my mind. I'm not seeing Dr. Mitchell or the NEDU team jumping in here to support your case
