Mismatched dive computer nitrox settings and SAC

[Linus Torvalds]

On Sun, Oct 10, 2021 at 6:24 AM Michael Andreen via subsurface
<subsurface at subsurface-divelog.org> wrote:
>
> it would be nice to have some way of setting this bogus cylinder as not used.

So the problem is that it is marked as used by one of your dive
computers, and as a result subsurface refuses to delete it.

It would be easy to edit the dive file to set the sensor ID to the
single tank yuou want to keep - and then you'd be able to delete the
now truly unused cylinder - but we don't have any GUI interface to
edit those kinds of details.

There's a lot like that where we just don't have any UI to edit
low-level stuff.

One thing you can do next time you realize what is going on, is to
download the dive from one dive computer, then *edit* the gas mix to
match the second dive computer, and then download it from the second
dive computer. Then you won't end up with two cylinders due to having
two different mixes.

In fact, you can use that same trick to "fix" it now:

 - right-click on the dive computer name in the profile window

 - select "Split this dive computer into its own dive"

 - now you have two dives, each with two cylinders, but now only one
dive computer.

 - Now only one of the cylinders is actually used for each dive, and
you can remove the unused one.

 - you can merge them together again, only having one cylinder.

HOWEVER! I wouldn't be at all surprised if the above "fix" doesn't
actually work, because we often end up getting confused about the
sensor indexes when doling things like this. So it's not at all
unlikely that playing the above kinds of games will then result in the
air integrated pressure readings being lost, and you actually end up
with more problems than you started with.

Sensor pressure data when there are multiple cylinders (and we think
multiple sensors) is definitely an area we end up often having
problems with.

So fixing it proactively (ie editing the cylinder O2 percentage to
match before downloading the second dive) is most definitely the thing
that actually works.

Or you can edit the xml or git save file directly, and avoid all the
UI issues. The format isn't that complicated, but yeah, I say that as
somebody who actually looks at those files quite regularly.

               Linus