[Patch] Fix planner notes gas change output logic

Rick Walsh rickmwalsh at gmail.com
Wed Jun 17 23:49:20 PDT 2015


Thanks for the feedback,

On 18 June 2015 at 16:16, Robert C. Helling <robert at euve10195.vserver.de>
wrote:

> Hi,
>
>
>
> Am 18.06.2015 um 02:09 schrieb Rick Walsh <rickmwalsh at gmail.com>:
>
> However, I think a more intuitive output would be:
>
> depth dur. runtime gas
> 20m 1min 1min air
> 20m 5min 5min
> 20m 10min 15min EAN80
> 20m 5min 20min air
> 9m 1min 21min <-for the segment of 1min duration leading up to the 21min
> runtime (we ascend to 9m), we are still breathing air
> 9m 0min 21min EAN80 <-there is zero time at 9m, but this is where to
> change to EAN80
> 6m 17min 39min <-keep breathing EAN80
> 0m 2min 41min
>
> Do you think this is a clear and reasonable approach?
>
>
> This is definitely a correct approach. It is not what I had in mind,
> though, but it is very close. These notes are supposedly copied to wet
> notes and taken underwater. So, to avoid task overloading, the display
> should really be minimal and contain no clutter.
>
> A 0min stop looks a bit weird to me. So my plan was to merge that segment
> with the preceding transition an thus place the ean80 there.
>


> After all, the printed gas indicates the diver should do a gas switch.
>
> Look at it from this point of view: the table row.
>
> 9m x min y min EANzz
>
> Should really be read as the instruction to the diver:
>
> Go to 9m. There switch to the gas. Then stay there until runtime y. Then
> go to the next line.
>
> At least that supports my intended way of doing things.
>
> BTW this whole discussion is a bit academic: gas switches without stop
> that we are worrying about do not appear in real dives. As no stops come
> with short shallow dives for which you would not take additional gases. Or
> we could resolve it by stating a gas change is automatically followed by a
> stop of at least one minute. After all the gas change takes some time. Not
> to mention esoteric topics like the oxygen window.
>
>
I agree we're getting a bit academic.  My problem with the gas change on an
ascent only segment with a duration is that being consistent with the other
stops, it implies we should be breathing that gas for that duration (i.e.
on the ascent).  For the option ignoring transitions, what do you think of
having a zero duration segment, but not including the preceding ascent
segment.  That way we put the gas change at the correct depth, but indicate
by a zero duration that there isn't a stop required.

E.g.

20m 5min 20min air
9m 0min 21min EAN80 <-there is zero time at 9m, but this is where to change
to EAN80
6m 17min 39min <-keep breathing EAN80
0m 2min 41min



There are real cases where the gas change is done when a stop (for a
duration) is not required.  I'm halfway through an Advanced Nitrox and Deco
Procedures course, which is largely why I'm suddenly paying more attention
to dive planning.  On two dives last week, I had a ceiling of 12 m at the
end of my bottom time.  Deco gas was 50% - so there was a gas change at 21
m, but a stop wasn't required.  I did stop to switch gas, but it is
technically possible to start the procedure during ascent, and do the
actual switch without stopping for longer than a few seconds.



> Best
> Robert
>
> Ps: this is probably the longest email I ever typed on the phone.
>

Ouch. Thanks for the effort.

Rick
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