Log import of Trimix dive from Shearwater Teric

[Attilla de Groot]

> On 8 Oct 2021, at 15:53, Linus Torvalds <torvalds at linux-foundation.org> wrote:
> 
> On Fri, Oct 8, 2021 at 11:50 AM Attilla de Groot via subsurface
> <subsurface at subsurface-divelog.org> wrote:
> 
>> Logging:
>> - Subsurface doesn’t understand the concept of a travel gas that well (it switches with the back gas).
> 
> Heh. That example dive looks _very_ different from anything I ever did
> in Bonaire.

My dives this week are quite exceptional indeed. Next week I’ll just do some recreational and looking at fish. :-P

> 
> But your data clearly has
> 
>  <cylinder size='22.2 l' workpressure='232.0 bar' description='D12
> 232 bar' o2='14.0%' he='49.0%' depth='65.378 m' />
>  <cylinder size='4.1 l' workpressure='206.843 bar' description='AL40'
> start='220.0 bar' end='140.0 bar' depth='103.075 m' />
>  <cylinder size='5.547 l' workpressure='206.843 bar'
> description='AL40' o2='51.0%' start='200.0 bar' end='140.0 bar'
> depth='21.021 m' />
>  <cylinder size='5.547 l' workpressure='206.843 bar'
> description='AL40' o2='79.0%' start='175.0 bar' end='90.0 bar'
> depth='10.016 m' />
> 
>  <event time='0:02 min' type='25' flags='1' name='gaschange'
> cylinder='0' o2='14.0%' he='49.0%' />
>  <event time='3:26 min' type='25' flags='2' name='gaschange' cylinder='1' />
>  <event time='30:32 min' type='25' flags='3' name='gaschange'
> cylinder='2' o2='51.0%' />
>  <event time='44:40 min' type='25' flags='4' name='gaschange'
> cylinder='3' o2='79.0%' />
> 
> which I agree is insane - you are going down to 82m and subsurface
> thinks you're breathing air at the deepest point (and breathing that
> hypoxic 49% He at the beginning shallow part).
> 
> That would be unhealthy and bad if real. I agree that clearly the two
> first gases are switched.
> 
> However, subsurface thinks that because those are the gas switch events we got.

Is it possible to manually change this to how it should be (given that you’re explaining it must be a download/libdivecomputer issue)? I messed around with it a bit, but I don’t really understand the relation between the cylinders and gas changes in the XML. I haven’t been able to make it any better unfortunately.


> And I have to say, when I tell subsurface to use the same 55/85
> Buehlmann settings that your dive computer reports it is using, the
> deco that subsurface calculates isn't actually that far off from what
> your Teric calculated. In fact, if anything, your Teric gave _more_
> deco at the end.
> 
> That said, that can't be real, and I suspect the issue is that I only
> see the one dive, and you presumably had some pre-existing deco
> loading, and then subsurface getting the gases wrong just happens to
> result in a fairly similar deco profile.

That is fine, should I see it again sometime, I’ll bring it up separately.

> I'll think about this a bit more to see if I can come up with
> something, but I hope I have explained why it can be hard due to
> libdivecomputer explicitly making it hard.

Thank you, much appreciated.


— Attilla