Dive planning for caves

[Rick Walsh]

On 17 Jun 2016 16:42, "Willem Ferguson" <willemferguson at zoology.up.ac.za>
wrote:
>
> Robert,
>
> 1) When diving caves, a large part of the dive profile has to be "hard
coded" because of the physical characteristics of the cave system. For
instance, see the attached image, planned for deco using both EAN50 and
oxygen. This cave system has three levels at 17m, 26m and 36m. The descent
to the lowest level , as well as the ascent from the lowest level, is
determined by the physical necessity to swim horizontally at each level,
and, in addition, by the time required to fasten and lay lines. Thus a
minimum-level dive plan to the 36m level may perhaps resemble the attached
graph. However, on ascent, I would have liked the planner to recommend
switching to EAN50 somewhere between the 26m and 17m levels, not at the end
of the 17m level. (Normally, one would leave the EAN50 cylinder at the exit
of the 26m level, pick it up on ascent and do the gas switch during the
transition from the 26m level to the 17m level). It looks like the planner
only starts calculating gas switches after the last "hard-coded" segment at
17m, not before. The switching sequence during ascent, from back gas to
EAN50 to Oxygen, is a mess. Moreover, one cannot force a switch to EAN50 by
right-clicking the last "hard-coded" point at 17m on the profile because
there is no option to specify a gas switch when right-clicking that last
point. When using the planner, is there an easy way around this problem?
>
> 2) Of course, a solution is to "hard-code" a switching point at around
21m and then force a gas switch. But I encounter a lot of problems with
this. When I force a gas switch to EAN50, it erroneously inserts a switch
to Oxygen, not EAN50. I can play around a bit, eventually forcing the gas
switches to be correct, but the indication of cylinder pressure (P in the
black info box) disappears.
>
I usually specify the "hard-coded" part of the plan, including gasses and
depths, using the waypoints table. The leg to 21m should be using your
bottom gas. The leg from 21m to 17 (and the constant 17m) select 50%.

Trying to code the logic of gas switches into the entered points is a bit
complicated. In your example it could be done, but what if the user wants
to override the selection? A tougher example would be a cave that requires
ascents and descents to exit, so that you go shallower than you switch
depth before going deeper.

> 3) In addition, when working with different cave dive plans in the above
way and I select "Cancel" dive plan, I get a segfault.
>
> If there is any way that I can help you, e.g. specifying sequences to
generate any of the conditions I mention above, I would gladly oblige.
>
This sounds a lot like a segfault I encountered, and Linus fixed. Can you
see if it works with latest master/daily? If not, can you run in gdb and
get a backtrace?

Cheers,

Rick
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