SAC Rate for Sidemount

[John Van Ostrand]

Subsurface calculates SAC rate based on tanks that have been used on the
dive and will ignore other tanks listed in equipment. Until I realized this
I thought my consumption which I had worked hard to reduce on that dive had
improved. This could have been dangerous had I not questioned it.

As a sidemount diver I switch tanks regularly during a dive and don't
record the run time and pressure when the switch happens. It's not typical
to do so. I also don't have a gas pressure integrated dive computer.

I can work around this either by declaring my tank to be 200 cu ft, by
declaring a working pressure of 474 bar, or by inserting at least one tank
switch.

I understand that the current method is a clean solution but I'm not sure
it's practical. A user could get into trouble if they trusted the SAC rate
without knowing that the second tank wasn't included.

Solutions might be:

1. List all tanks with start/end pressure on the Info page and list their
individual SAC rates. Display a total (i.e. effective) SAC rate. This gives
the user the most conservative SAC rate but also allows them to mentally
remove a tank (like Argon) that isn't used for breathing. Show effective
SAC on the graph.

2. List all tanks with pressures on the info page and note tanks that were
not explicitly used. SAC rate on graph would remain as is.

3. Warn the user somehow that a tank in the equipment list appears to be
used but isn't explicitly used.

Thoughts?

-- 
John Van Ostrand
At large on sabbatical
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