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<p>Hello Willem,<br>
</p>
<br>
<div class="moz-cite-prefix">Am 18.10.2017 um 06:06 schrieb Willem
Ferguson:<br>
</div>
<blockquote type="cite"
cite="mid:7c65712f-2a34-9f4b-f4e7-4fa273505280@zoology.up.ac.za">On
17/10/2017 22:37, Stefan Fuchs wrote:
<br>
<blockquote type="cite">
<br>
Now about the "5bar" result from your first plot. Yes, this
makes no real sense. Root cause is that my implementation
currently always does the calculation for the last manually
entered data point and this in your case is at 22m. This is so
close to the possible gas change at 21m that almost no gas
volume is needed to go there. It would be correct in this case
to do the calculation for the second last entered data point at
40m. But implementing this is not so easy because there could be
also the use case of a multi level dive with some bottom time at
60m and then some more bottom time at 45m. Here we would really
need to check at which point of the dive (deeper depth vs.
longer bottom time!) the situation is most critical.
<br>
For your simple example I have an easy proposal: Remove the last
data point and let the planner do the complete ascend starting
from 40m.
<br>
For your "plan2" the results look almost good and I even tend to
remember that I did use bottom SAC and deco SAC according to
your proposal:
<br>
Ascend: 27bar*2 = 54bar
<br>
Problem solving: 1min*20l/min*2*9=270l ~ 15bar
<br>
Total would be 69bar, printed is 67bar... hmm, is this the
compressability thing once again or just comes from rounding - I
have to double check this.
<br>
Ah, you did look at the green delta value again - I have to
think about the green value! ;-)
<br>
<br>
<br>
Please feel free to provide more examples and comments! I will
think about possible improvements.
<br>
<br>
Best regards
<br>
Stefan
<br>
</blockquote>
<br>
Hallo Stefan,
<br>
<br>
Let me just make sure, the green value is the minimum cylinder
pressure when starting the ascent. This takes into account the
minimum gas as well as another externally-specified minimum
cylinder pressure. If it gives the green value as 159 bars and the
minimum gas as 5 bars, where do the other 154 bars come from?
There is a strong case for good documentation here.
<br>
<br>
</blockquote>
No, much easier: <br>
The value in black is the minimum gas result based on the
calculation described above. Let's assume it's 90bar in another
example.<br>
The value which currently is printed in green or red with the
"Delta" symbol in front in simply the delta between the 90bar and
the cylinder pressure you have left at the same moment. Let's assume
based on the cylinder pressure calculation you have 110bar left. So
the Dealt is +20bar. That means for you, you could plan a even
longer bottom time. If the Delta is negative you should reduce
bottom time.<br>
<br>
Well, ok, I put on my ToDo list:<br>
- Change syntax at least slightly (maybe change the color thing)<br>
- DOCUMENTATION <br>
<br>
<blockquote type="cite"
cite="mid:7c65712f-2a34-9f4b-f4e7-4fa273505280@zoology.up.ac.za">The
problem comes with cave dives where the geometry of the cave
determines much of the ascent. In these cases it is necessary to
specify at least part of the ascent to allow sufficient time to
swim through the cave on the way up. In my typical case the cave
entrance is at 15m where it opens into open water so this does not
give the dive planner a lot of scope to do any useful calculation.
In some perverse sense one may describe this as a multilevel dive.
I attach a profile where these intermediate steps are pretty
evident and where the ascent was specified to 15m in the dive
plan. However, in this case the minimum gas calculation would be
more meaningful if it were applied to the end of the bottom
section and not at the point of exiting the cave at 15m. The
problem then is, as you note, to distinguish between a multilevel
dive and one that is not intended as multilevel. I wonder whether
it would be possible to identify a "bottom gas", maybe the one
that has the lowest fraction of oxygen (FO2) and do the minimum
gas calculation for that gas mix. For an intended multilevel dive
(say 10 min at 45m, 20 min at 30m), it would give the worst case
minimum gas applicable to the deepest part of the dive.
<br>
</blockquote>
Understood. I will think about a possible solution for this. But
this may clearly involve also switching off minimum gas calculation
in cases where the result is meaningless. And this will come after
4.7 :-)<br>
<br>
<br>
Your feedback helps me a lot to understand user needs and to improve
things. I already yesterday identified one use case for the cylinder
handling where I missed s.th. Next small PR will follow...<br>
<br>
<br>
Best regards<br>
Stefan<br>
<br>
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<p>Stefan Fuchs<br>
E-Mail: <a href="mailto:sfuchs@gmx.de">sfuchs@gmx.de</a></p>
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