Subsurface planner

Sun Oct 15 23:59:33 PDT 2017

Hi Willem,
On 16 October 2017 at 16:32, Willem Ferguson <
willemferguson at zoology.up.ac.za> wrote:

> Robert, Stefan,
>
> After your recent work on the planner, has anything changed in the planner
> UI or the way it functions? I do not see anything but I can hardly think
> that this could be the case after all your work.
>
> There are only two feature changes in the planner that I'm aware of:

1) Plan variations (Robert).  Activated by notes option "Display plan
variations", it prints the rate of difference in decompression time
required for increasing/reducing the bottom time and depth.  This is an
advanced feature of the planner, useful for on-the-fly estimates (and
theoretical considerations/comparisons) of required decompression for small
adjustments to bottom time and/or depth, and an alternative to writing out
several plan contingencies.

Using the feature for contingency planning, it is up to the diver to decide
where the time should be added  / subtracted (and of course whether they
are comfortable with this method of calculating plan variations).  The
relationships between bottom time and depth, and decompression time are not
linear in general, but for small adjustments linear approximation is
reasonable.  In the example below, the plan variations line says that
changing the dive depth leads to change in required decompression time by
+/-1:30 per metre, and varying bottom time changes required decompression
time by +/- 1:26 per minute. If the diver gets to the bottom and realises
the depth is only 38m (not the 40m planned), the diver could choose to
reduce decompression by 2m * 1:32 /m = 3:04 ~ 3min.  E.g. the diver could
decide to reduce the 6m stop by 2min, and the 12m stop by 1min.
Alternatively, the diver could choose to extend the bottom time by 2min
(leading to an increase in decompression time of 2 * 1:27 = 2:54 ~ 3min),
and follow the original decompression schedule.

Subsurface (4.6.4.986) dive plan created on 10/16/17
Runtime: 57min + 1:32 /m + 1:27 /min

depth

duration

runtime

gas

➘

40m

2min

2min

(21/35)

➙

40m

28min

30min

➚

21m

2min

32min

-

21m

1min

33min

EAN50

-

12m

3min

36min

-

9m

3min

39min

-

6m

18min

57min

➚

0m

1min

58min

CNS: 21%
OTU: 59

Deco model: Bühlmann ZHL-16C with GFLow = 40% and GFHigh = 85%
ATM pressure: 1013mbar (0m)

Gas consumption (based on SAC 20|20ℓ/min):
3078ℓ/136bar of (21/35) (172ℓ/7bar in planned ascent)
 — Minimum gas (based on 3.0xSAC/+2min at 40m): 1124ℓ/47bar/Δ:+57bar
904ℓ/82bar of EAN50 (904ℓ/86bar in planned ascent)

Comparison with 2m shallower dive plan - note this is the same as taking
2min from the 6m stop, and 1min from the 12m stop from the 40m
decompression schedule

Subsurface (4.6.4.986) dive plan created on 10/16/17
Runtime: 54min + 1:19 /m + 1:10 /min

depth

duration

runtime

gas

➘

38m

2min

2min

(21/35)

➙

38m

28min

30min

➚

21m

2min

32min

-

21m

1min

33min

EAN50

-

12m

2min

35min

-

9m

3min

38min

-

6m

16min

54min

➚

0m

1min

55min

Comparison with 2m shallower and 2min longer bottom time plan - note this
is nearly the same (1min less on final stop) as the 40m 30min dive plan
decompression schedule

Subsurface (4.6.4.986) dive plan created on 10/16/17
Runtime: 58min + 1:34 /m + 1:21 /min

depth

duration

runtime

gas

➘

38m

2min

2min

(21/35)

➙

38m

30min

32min

➚

21m

2min

34min

-

21m

1min

35min

EAN50

-

12m

3min

38min

-

9m

3min

41min

-

6m

17min

58min

➚

0m

1min

59min

I'm hoping this could be explained more concisely in the user manual.
Robert?

2) Minimum gas pressure delta (Stefan)
I think this feature is great, but unfortunately not intuitive.  I only
worked out what it meant by reading the commit diff.  It should be
documented in the user manual.  It tells you how much gas you should have
in reserve at the end of your bottom time in excess of what is required for
the calculated Minimum Gas.  From the example above
 — Minimum gas (based on 3.0xSAC/+2min at 40m): 1124ℓ/47bar/Δ:+57bar
This tells the user they should have 57bar more than their Minimum Gas
requirement at the end of their planned bottom phase.

Like with the existing minimum gas calculation, it only applies when
cylinder sizes and pressures have been defined.

> The planning using VPM-B is still pretty broken. The ceiling generated is
> just totally wrong.

Can you please test the latest master / daily builds?  My commit f9d05a8 a
week ago should have corrected the *totally* wrong ceiling, but there may
be more bugs.  If it's still not right we need to fix that.

The issue "Deco ceiling calculation for EAN32 dive with 3m steps on/off -
very strange results #630" (
https://github.com/Subsurface-divelog/subsurface/issues/630) is still open,
but I can't reproduce it using Dirk's 4.6.4.986 Windows daily build.
Stefan, can you please confirm if it has been fixed, and if not provide
more detail what's wrong?

Cheers,

Rick
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.subsurface-divelog.org/pipermail/subsurface/attachments/20171016/fe4f9866/attachment-0001.html>