Re: Dive plan: Taking into account isobaric counterdiffusion

[Anton Lundin]

On 02 January, 2018 - Willem Ferguson wrote:

> We have
> had some serious injuries by ignorant divers who dived to 80m with
> trimix and who then used air as a deco gas. Crazy. Therefore I
> regard the ICD info as critical.
> 

My ICD management is simple, Never use Air as a deco gas[1]. Its just
a awful deco gas.

Joking aside, I use the pp graph's in subsurface for inert gas pp
management. Just make sure they don't rise above what you are saturated
on.


A comment on the IANTD rule of thumb, is that another one I've seen is
to never raise the inert gas pressure by more than 0.5 on a gas change.
From what I've read V-planner uses this rule.


Ex. on a 100m dive, on 10/70 , I wouldn't have any problem using 21/35
as the first deco gas, but I would probably throw in some extra he,
making it a 21/45 or something.


//Anton


1. Unless I'm doing a air dive, and mange to build up some deco time,
and don't have anything better around...


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Re: Dive plan: Taking into account isobaric counterdiffusion

[Stefan Fuchs]

Hallo Robert, hello Willem,


Am 02.01.2018 um 15:24 schrieb Robert Helling:
> Hi,
>
>> On 2. Jan 2018, at 14:53, Stefan Fuchs > > wrote:
>>
>> I am personally interested in this topic so I started to play with
>> your patch and this is my feedback:
>> - +1 for implementing s.th . regarding ICD / IBCD
>> - Ok with choosing this 5% rule of thumbs from IANTD unless someone
>> clearly shows us that there is a MUCH better approach or e.g. a kind
>> of 2nd/3rd/... limit we could consider additionally
>> - No real idea where else we could put this code other than in the
>> plannernotes.c
>> Ok, this was the easy part, now the more difficult items:
>> - I already expected people to give negative feedback regarding
>> cluttering the UI/output - and I would have understood this.
>> Always adding this additional column in the dive plan table with some
>> complex info which is needed by almost nobody really doesn't look
>> that nice. So we need to look for a clever solution for this. I
>> already see a few options:
>> x Only show this column for Tx dives (not too difficult but still it
>> could happen that s.o. want's NOT to see the info)
>> x Prefs option to switch it on/off (yeah, also cluttering the UI)
>> x Don't print ICD info into plan/table but only show it as a tool tip
>> when hovering over the gas in the plan (complex, maybe even not possible)
>>
>
> I also like the idea of displaying the info on ICD (and I am happy to
> hear that there is some sort of limit that at least some people agree on).
Yeah, surprisingly already two or maybe even three people feel ok with
the same solution ;-)
BTW, it's the rule of "1/5", not as I accidentally wrote the rule of "5%".
Honestly I didn't hear of this rule until Willem mentioned it. But I
simply say "ok for me" because:
- IANTD afaik is not the least important tech diving association ;-)
- What I read about this rule of thumbs on the web makes sense
- The results simply fit together with my knowledge of what is a OK gas
combination and what is a NOT OK gas combination regarding ICD
  (not too difficult for me because the only two Tx bottom mix I "know"
are Tx21/35 and Tx18/45 and I know that EAN50 as 1st deco gas is OK
together with the Tx21/35 but NOT OK with the Tx18/45)
- Implementing the "rule" itself will finally maybe even not be the most
important/interesting part but showing dN2% and dHe% is much more
interesting - BTW, yes, I would also print dHe%

> I am not sure, the dive notes/written dive plan are the best location
> for the display, though, in particular since those notes are supposed
> to be printed on wet notes (and during the dive this is not relevant
> information). Wouldn’t it be better to make this an event in the
> profile or modify the gas change event accordingly (including the
> percentage information and maybe using a different icon if the change
> is above the threshold)?
Yes, goes on the list of possible solutions. But also Willems latest
proposal should go on the list.
And then we need to fill the decision form - hopefully Dirk installed a
process for this - sorry, working in a large company for too long time
already... ;-)

Best regards
Stefan

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Re: Dive plan: Taking into account isobaric counterdiffusion

[Willem Ferguson]

On 02/01/2018 16:24, Robert Helling wrote:

Hi,

On 2. Jan 2018, at 14:53, Stefan Fuchs > wrote:


I am personally interested in this topic so I started to play with 
your patch and this is my feedback:

- +1 for implementings.th . regarding ICD / IBCD
- Ok with choosing this 5% rule of thumbs from IANTD unless someone 
clearly shows us that there is a MUCH better approach or e.g. a kind 
of 2nd/3rd/... limit we could consider additionally
- No real idea where else we could put this code other than in the 
plannernotes.c

Ok, this was the easy part, now the more difficult items:
- I already expected people to give negative feedback regarding 
cluttering the UI/output - and I would have understood this.
Always adding this additional column in the dive plan table with some 
complex info which is needed by almost nobody really doesn't look 
that nice. So we need to look for a clever solution for this. I 
already see a few options:
x Only show this column for Tx dives (not too difficult but still it 
could happen that s.o. want's NOT to see the info)

x Prefs option to switch it on/off (yeah, also cluttering the UI)
x Don't print ICD info into plan/table but only show it as a tool tip 
when hovering over the gas in the plan (complex, maybe even not possible)




I also like the idea of displaying the info on ICD (and I am happy to 
hear that there is some sort of limit that at least some people agree on).


I am not sure, the dive notes/written dive plan are the best location 
for the display, though, in particular since those notes are supposed 
to be printed on wet notes (and during the dive this is not relevant 
information). Wouldn’t it be better to make this an event in the 
profile or modify the gas change event accordingly (including the 
percentage information and maybe using a different icon if the change 
is above the threshold)?


What do you think?

Best
Robert


Thank you, Stefan and Robert,

The current implementation only supplies the ICD information for OC dive 
plans that include trimix. I understand the argument about adding to the 
profile listing of the dive plan. What if one makes a separate paragraph 
at the bottom of the dive plan by adding a  small HTML table? Something 
like:


CNS: 78% OTU: 164 Deco model: Bühlmann ZHL-16C with GFLow = 33% and 
GFHigh = 66% ATM pressure: 899mbar (931m) Isobaric counterdiffusion 
information *Time    Gas change **ΔN₂ **Max ΔN₂* 12:13    11/55 -> 21/42 
        3.0%  2.6% 12:27    21/42 -> 33/31     3.0%      3.0% 
12:38    33/31 -> EAN55       5.0%       5.8% Gas consumption (based on 
SAC 21|15ℓ/min): 933ℓ/84bar of EAN55 (383ℓ/35bar in planned ascent) 
2506ℓ/110bar of (11/55) (676ℓ/30bar in planned ascent)  — Minimum gas 
(based on 2.0xSAC/+1min@115m): 1864ℓ/79bar/Δ:+51bar 1200ℓ/105bar of 
EAN80 (1200ℓ/108bar in planned ascent)  — Warning: not enough reserve 
for gas sharing on ascent! 836ℓ/79bar of (21/42) (371ℓ/36bar in planned 
ascent) 683ℓ/62bar of (33/27) (683ℓ/65bar in planned ascent) 0ℓ/0bar of 
oxygen I am not sure the alignment of this table will be ok in your mail 
browsers, but you will get the idea, I am sure. The table will only show 
for OC trimix dives. Having to hover over the profile to get the ICD 
information requires a lot of work for the user to get some very simple 
but critical information. My feeling is that the info, when relevant, 
should be immediately and prominently available. We have had some 
serious injuries by ignorant divers who dived to 80m with trimix and who 
then used air as a deco gas. Crazy. Therefore I regard the ICD info as 
critical.


I do not think one should go so far as to say "you are above the limit" 
and provide a YES or NO decision with respect to ICD. As with so many 
diving decisions, these are based on experience and track record, rather 
than hard scientific facts. My preference would be to show deltaN2 and 
Max_deltaN2 and allow the diver to make the decision of whether the 
differences in gas mixtures are within limits or not. (For instance the 
first change in the "table" above has deltaN2 of 3.0%, which is 0.4% 
more than Max_deltaN2. I *personally* would be happy with that 
difference, even though the difference is slightly larger than the 
maximal value of 2.6% because gas composition is also affected by gas 
mixes that allow accommodating failure of a deco gas during ascent, so 
there are competing factors that affect gas mixtures during the dive).


Please comment on these ideas!

Kind regards,

willem


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Re: Dive Planner: Inconsistent dive ceiling calculations

[Willem Ferguson]

On 02/01/2018 15:34, Robert Helling wrote:

Willem,

reading your second mail, I understand there are only two different 
ceilings left: The one in the divelist which equals the one in the 
planner when you remove the ascent points and the second one you get 
in reedit until you remove the ascent waypoints.


This is a „feature“ of the VPM-B model: It treats the „decompression 
phase“ different from the bottom part of the dive, in particular it 
takes note of the ceiling at the beginning of the decompression. In 
the planner (as well as replan), we take all the explicitly listed 
waypoints as the definition of „bottom phase“ (so in replan before 
deleting the waypoints, the whole dive is „bottom phase“). In the 
divelist we make a clever guess (thanks to Rick’s code) as to where 
the bottom phase ends. This tends to be very close to the true bottom 
phase of planned dives (when the entered waypoints end at the deepest 
part of the dive and then the planner takes over and manages the 
ascent) but is not exactly the same.


I have recently blogged about this problem here

https://thetheoreticaldiver.org/wordpress/index.php/2017/12/22/vpm-b-for-real-dives-or-not/

Best
Robert


Hi Robert,

It's such a pleasure interacting with someone who really understands 
this thing, because I do not. I will document this issue in the user 
manual. It's really the way that the representation in Subsurface 
interacts with the VPM algorithm when a dive plan is reloaded for editing.


Would there be a possibility of a user defining the end of the bottom 
section of the dive and for automatically clearing the ascent dive 
points when a plan is reloaded from the dive list for editing? I 
understand how arbitrary the "start of ascent" can be, e.g. when doing 
multi-level diving.


V-planner handles this problem in a bit of a different way. One can 
define predetermined segments (e.g. a multilevel dive or a cave dive) 
that cannot be avoided in the ascent. However, between these segments, 
V-Planner still calculates a deco schedule. For instance if a multilevel 
dive has two depths, e.g. 40m for 20 min; then 20m for 20 min, V-Planner 
still gives deco stops between 40m and 20m, even though there is a 
pre-determined 20min "stop" at 20m. It would be wonderful if Subsurface 
has a way of dealing with this situation. You have no idea how powerful 
the Subsurface dive planner is for rapid graphical assessment of gas 
volumes used, planning for possible failure of a deco cylinder and many 
other things. The graphical representation makes an enormous difference.


Thank you so much for your time.

Kind regards,

willem



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Re: Dive plan: Taking into account isobaric counterdiffusion

[Robert Helling]

Hi,

> On 2. Jan 2018, at 14:53, Stefan Fuchs  wrote:
> 
> I am personally interested in this topic so I started to play with your patch 
> and this is my feedback:
> - +1 for implementing s.th . regarding ICD / IBCD
> - Ok with choosing this 5% rule of thumbs from IANTD unless someone clearly 
> shows us that there is a MUCH better approach or e.g. a kind of 2nd/3rd/... 
> limit we could consider additionally
> - No real idea where else we could put this code other than in the 
> plannernotes.c
> Ok, this was the easy part, now the more difficult items:
> - I already expected people to give negative feedback regarding cluttering 
> the UI/output - and I would have understood this.
> Always adding this additional column in the dive plan table with some complex 
> info which is needed by almost nobody really doesn't look that nice. So we 
> need to look for a clever solution for this. I already see a few options:
> x Only show this column for Tx dives (not too difficult but still it could 
> happen that s.o. want's NOT to see the info)
> x Prefs option to switch it on/off (yeah, also cluttering the UI)
> x Don't print ICD info into plan/table but only show it as a tool tip when 
> hovering over the gas in the plan (complex, maybe even not possible)
> 

I also like the idea of displaying the info on ICD (and I am happy to hear that 
there is some sort of limit that at least some people agree on).

I am not sure, the dive notes/written dive plan are the best location for the 
display, though, in particular since those notes are supposed to be printed on 
wet notes (and during the dive this is not relevant information). Wouldn’t it 
be better to make this an event in the profile or modify the gas change event 
accordingly (including the percentage information and maybe using a different 
icon if the change is above the threshold)?

What do you think?

Best
Robert


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Re: Dive Planner: Inconsistent dive ceiling calculations

[Robert Helling]

Willem,

> On 2. Jan 2018, at 13:57, Willem Ferguson  
> wrote:
> 
> Attached four files: a dive plan and three profiles.
> 
> 1) Load dive plan into Subsurface. This gives dive1_list.png.
> 
> 2) Open the dive plan for edit in the planner. This gives dive1_2.png. A 
> totally different ceiling compared to previous representation.
> 
> 3) Delete all the dive points in the ascent phase of the dive plan. I used 
> the Dive Points Table to delete the points. This gives dive1_3.png. Yet 
> another ceiling totally different from previous representation.
> 
> We have three entirely different ceilings for the same dive plan.
> 
> I have no idea where the inconsistency arises.

reading your second mail, I understand there are only two different ceilings 
left: The one in the divelist which equals the one in the planner when you 
remove the ascent points and the second one you get in reedit until you remove 
the ascent waypoints.

This is a „feature“ of the VPM-B model: It treats the „decompression phase“ 
different from the bottom part of the dive, in particular it takes note of the 
ceiling at the beginning of the decompression. In the planner (as well as 
replan), we take all the explicitly listed waypoints as the definition of 
„bottom phase“ (so in replan before deleting the waypoints, the whole dive is 
„bottom phase“). In the divelist we make a clever guess (thanks to Rick’s code) 
as to where the bottom phase ends. This tends to be very close to the true 
bottom phase of planned dives (when the entered waypoints end at the deepest 
part of the dive and then the planner takes over and manages the ascent) but is 
not exactly the same.

I have recently blogged about this problem here

https://thetheoreticaldiver.org/wordpress/index.php/2017/12/22/vpm-b-for-real-dives-or-not/
 


Best
Robert


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Dive Planner: Inconsistent dive ceiling calculations

[Willem Ferguson]

I solved one of the anomalies. When opened in the dive list, a Bühlmann 
ceiling is shown, determined by the default presentation in my Preferences.


However, the dive is a VPM-B dive plan. When opened for edit, the VPM-B 
ceiling is shown. But this does not explain the differences in the last 
two of the profiles in the last mail on this issue.


By the way, there is no problem with the Bühlmann version of this same 
dive plan, being shown correctly during all phases of editing the dive plan.


Kind regards,

willem



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