Multiple tanks from divelogs

[Rainer Mohr]

Hi Miika,

Am 28.01.15 um 05:13 schrieb Miika Turkia:
> If I open your sample dive on Subsurface, I get two tanks in the 
> equipment tab. As there is no gas change event to the EAN95 cylinder, 
> the upload to divelogs.de <http://divelogs.de> ignores this cylinder. 
> (We had a complaint at some point that unused cylinders get uploaded - 
> this was probably due to some DCs reporting more cylinders than was 
> already used during a dive.)
>
> When I add a gas change in Subsurface, upload to divelogs.de 
> <http://divelogs.de> includes both of these cylinders. Do you support 
> any events in your XML format? The gas changes are lost in the upload 
> and thus we end up back with only one used gas if downloaded again to 
> Subsurface.

Here's a point where I would suggest to generally handle this differently...
IMHO, the gas change event is not suitable for deciding if a gas has 
been used or not.

Think of the growing number of sidemount divers. They use 2 separate 
tanks with a reg each, mostly filled with the same gas. They switch regs 
several times throughout the dive, but don't do the gas switch in their 
computers, because there is no need for that (same gas).

Or take the people with computer models, that don't support multiple 
gasses. They might still do their deco with a second nitrox tank or even 
pure oxygen for safety reasons, but don't have a possibility to document 
the switch in their computer.... but they will still want to document 
this in subsurface.

All these examples would get a wrong SAC, because the other tanks have 
not been considered, although they breathed from them.

Why not simply check if the endpressure of a tank is lower than the 
startpressure to decide if a tank has been used? If the pressure changes 
by more than say 3% (to compensate pressure changes from temperature), 
it must have been used... No error I can see using this approach, as 
pressures per tank are entered individually for each dive.

This criteria could be used to decide which tanks to export and import 
(or which tanks to show in the list)

> I assume, you have not selected the "show unused cylinders in 
> equipment tab" as you are not seeing the EAN95.

OK, i see them now. Thanks. Was not aware of this

But I would still suggest to use another approach, see above. Your 
thoughts? Dirk? Linus?

Thanks as always,
Rainer
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