[PATCHES] Vary undersaturated portion of heatmap according inert gas

[Hartley Horwitz]

>
> ---------- Forwarded message ----------
> From: Rick Walsh <rickmwalsh at gmail.com>
> To: Robert Helling <helling at atdotde.de>
> Cc: "subsurface at subsurface-divelog.org" <subsurface at subsurface-divelog.org
> >
> Date: Wed, 19 Oct 2016 08:48:57 +1100
> Subject: Re: [PATCHES] Vary undersaturated portion of heatmap according
> inert gas
>
>
> On 18 October 2016 at 20:55, Robert Helling <helling at atdotde.de> wrote:
>
>> Will try. I definitely like patch 2, that’s a no-brainer.
>>
>> For patch 1, I see your point (the user can see if on-gasing is
>> happening). I am not yet convinced, though. the trouble I am having is
>> “what is the heat-map supposed to show?”. I think, it should be a measure
>> of deco quality (I argued for this when answering if it depends on the deco
>> model used, and no, it does not depend on VPM and not on the gradient
>> factors chosen). So, and I think this is a philosophical question, should
>> it depend on what the diver is breathing?
>>
>
I agree with Rick that I was expecting the heat map to show me a benefit
when comparing a nitrox dive to an air dive with the same profile.  I think
if two dives are at the same END then you'd expect the on-gassing to occur
equally and thus the heat map to reflect that.

That being said, if you load up a tissue compartment to equal ambient
(black), then when you rapidly rise to 6m (for example), the initial colour
should be the same, regardless of the gas mix you're breathing, and it
should show you are off-gassing.  The gas mix should reflect how quickly
you move from yellow (or white) to green, but shouldn't reflect the colour
at the beginning of off-gassing.


> Without that patch it is only about the state of the gases in the diver’s
>> body (and not about the time derivative as in on- vs. off-gassing). It
>> shows the potential for bubble formation (at least that is what it is
>> supposed to show). If we do it relative to then breathing gas, then it is
>> more about the time derivative.
>>
>> I am not really against it, just need a bit more convincing.
>>
>
> ........
>


> Compare a dive on 40% nitrox to 24m with a dive on air to 24m.  On
> reaching 24m, the rate of on-gassing is much faster with the air dive, but
> the colours are shown the exactly same if we do not adjust the heatmap
> according to the breathing gas inert gas pressure.
>

Agreed.

>
> Now consider an air dive to 16m (equivalent air depth of a dive to 24m on
> 40% nitrox).  Theory says the on-gassing is exactly the same as the deeper
> nitrox dive, so it makes sense to show the same colours on the heatmap.  If
> we take the patch to vary colours according to the breathed inert gas
> pressure (and descent and ascent take the same time), then the same heatmap
> is shown, which I think is helpful.
>
> ...Hartley Horwitz
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