Fwd: Re: [subsurface-4.7.8-81-gb930c39eade0] issue on displaying GF

[Willem Ferguson]

On 26/04/2018 10:53, Chirana Gheorghita Eugeniu Theodor wrote:
> Yes I figured that out , but would pose more sense if there would be 
> no subsurface setting in this matter. It makes no sense to setup the 
> dive log to display 30/75 when the dive computer reports it was using 
> 30/70 for that dive. Even more what if during a dive I change the GF 
> settings on the computer (which is possible on th eshearwater)??? what 
> will subsurface than display? it should display a icon in the dive 
> profile just like a cylinder change. Right?
>
> On Thu, Apr 26, 2018 at 11:37 AM, Willem Ferguson 
> <willemferguson at zoology.up.ac.za 
> <mailto:willemferguson at zoology.up.ac.za>> wrote:
>
>     On 26/04/2018 10:18, Chirana Gheorghita Eugeniu Theodor wrote:
>>     Please ignore this. It was from the general settings of the
>>     application...
>>
>>     On Thu, Apr 26, 2018 at 11:14 AM, Chirana Gheorghita Eugeniu
>>     Theodor <office at adaptcom.ro <mailto:office at adaptcom.ro>> wrote:
>>
>>         I have this dive opened on the windows version of libdcNG
>>         continuous build 4.7.8-81-gb930c39eade0. I see the dive
>>         computer setup as GF30/70 but in the dive profile screen it
>>         shows GF30/75. Issue of display glitch? Please see attached
>>         screenshot.
>>
>>         What is the "official"  release of the NG that is beeing
>>         maintained? Maibe I am using the wrong one?
>>
>     I suspect here the GF on the left (30/70) is the gradient factor
>     that the dive computer used. This is a function of the dive
>     computer settings. The value on the right (30/75) is  the GF that
>     Subsurface has been set to in the Subsurface Preferences (i.e. the
>     displayed profile GF).
>     Kind regards,
>     willem
>

I am not sure that this is generally doable.

Firstly, only a handful dc's record GF. Most do not. How should one deal 
with the dc's that do not record GF? How should one provide for the 
multiple ways in which different dive computers determine conservatism? 
Most dc's use conservatism levels, not GF.

Secondly, how is GF recorded in the Subsurface dive log? This is a 
function of the way libdivecomputer extracts data from the dive 
computer. I am not convinced that libdivecomputer has the ability to 
capture on-the-fly changes in GF during a dive, so your suggestion is 
probably not possible anyway. My Uwatec automatically adjusts the 
conservatism if the diver oversteps the deco requirements, but this is 
not captured by libdivecomputer. And I do not care too much about that.  
If this is a critical factor for you, then consider a dc like Shearwater 
that provides its own set of dive ceilings for each dive, reflecting the 
GF settings of the dc, including on-the-fly changes in GF. 
Libdivecomputer captures that perfectly.

Thirdly, the displayed GF in the Subsurface dive profile is a broad and 
general yard stick to evaluate the deco during the dive. Is it really 
crucial to modify the ceiling in a detailed way to reflect GF changes 
during the dive? All the a diver wants to do is to get a reasonable 
*overall* impression of how well the deco went in terms of tissue 
compartment gas pressures.

Kind regards,
willem


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