What's your SurfGF and how does it compare to your (Rec) GFHi?

[BlueTrin]

I think what you mean is already there, here how the end of my latest dive looks like:
View attachment 739769

Now since we have this already, what I am talking about is to add this number to the other dive info (like SAC, Water temperature, duration etc), so that the user can further use it for dive analysis (compare it among dives, do statistics, short dives based on this, see how it evolved over the years etc).
Since the number and the means to do all these analyses are already there, it is a pity not to be able to do that especially given that this particular metric seems to be so important.

Is there a setting to add it on the mobile version?

 

[Wibble]

Following this incredibly useful thread I would like to invite @dirkhh et al. to consider including in Subsurface's dive statistics the GF at the end of the dive ("end GF" or whatever it is called).
As this number is a good indication of how "aggressive" the dive was,

The SurfGF at the end of the dive will always be less than the GF-hi. Considerably less if it’s well under the Non-Deco-Limit**

All SurfGF shows is the amount of decompression obligation you have at any particular point in the dive. It is not a measure of "aggressiveness".

It would be great if Shearwater Cloud and SubSurface would display the SurfGF calculation for all points of the dive, maybe as a graph so you can see the SurfGF increase and decrease throughout the dive and decompression phase.


**edited, thanks @inquisit, @dmaziuk

 

[dmaziuk]

The SurfGF at the end of the dive will always be just under the GF-hi unless you’ve extended your stop after your decompression has cleared.

Under: yes, just: not necessarily. See Craig's post. (Of course one can argue that 80 is just under 95 for some values of "just".)

 

[hammet]

Yes. This has always confused me. What does "instantly" mean in practical terms?

I would think the computer just sets ambientpressure=surfacepressure.

 

[inquis]

The SurfGF at the end of the dive will always be just under the GF-hi unless you’ve extended your stop after your decompression has cleared.

Not all dives are to the NDL limit or beyond.

 

[stepfen]

The SurfGF at the end of the dive will always be just under the GF-hi unless you’ve extended your stop after your decompression has cleared.

Not really, unless somebody rides NDL. Rec divers usually don't (or should I say shouldn't?). The profile I uploaded above has no deco for the commonly used GFHi 85 (in the graph a bit of deco is shown because I had subsurface use 30/70). Then I spend ~10 minutes around 6m/20ft looking at a school of fish and doing some drills and stuff as I usually do, not necessarily having "safety" in my mind and GF at the end of the dive dropped to about 52-53%. Should I had just completed a 3min SS instead, I would have ended with a GF around maybe 70%. And this is exactly the point I think.

All SurfGF shows is the amount of decompression obligation you have at any particular point in the dive. It isn’t a measure of "aggressiveness".

In general through the dive SurfGF indicates gas loading indeed, but GF at the end of the dive, I think is an indication of aggressiveness. Ending at 95% seems more aggressive than ending at 80% or 60%, isn't it?

What would be interesting would be an ongoing SurfGF calculation for all points of the dive. I find it interesting to watch it slowly diminish throughout the decompression phase.

That's already implemented in Subsurface. The info box I showed in the profile above updates for all the points in the dive profile.
Of course, we that don't dive computers that show SurfGF we don't have this info in real time during the dive, but even seeing this post dive in Subsurface is of high interest.

 

[LFMarm]

I would agree that the final SurfGF (which is also equal to GF99 at the surface) is a measure of aggressiveness because it tells you how much Inert gas loading you still have at the end of the dive compared in percentage to regular Buhlmann

 

[Wibble]

I would agree that the final SurfGF (which is also equal to GF99 at the surface) is a measure of aggressiveness because it tells you how much Inert gas loading you still have at the end of the dive compared in percentage to regular Buhlmann

Question:
Would someone surfacing, say, with GF95 after a NDL dive be as aggressive as someone surfacing with GF95 after 2 hours of decompression?

One would think that the latter has some slow compartments heavily loaded, albeit below 95, compared with the former who has virtually no loading of slow compartments?

 

[stuartv]

Personally I think if you want to see that: just turn on the heat map. Unlike Surfer GirlFriend it shows you all compartments, and throughout the entire dive too.

I got the same answer to the same question in the past. The problem is I want numbers. The heat map doesn't give me that.

Question:
Would someone surfacing, say, with GF95 after a NDL dive be as aggressive as someone surfacing with GF95 after 2 hours of decompression?

One would think that the latter has some slow compartments heavily loaded, albeit below 95, compared with the former who has virtually no loading of slow compartments?

They are different. A different compartment will be the "controlling compartment" in one scenario versus the other.

Which one is more aggressive depends on the individual. One person might be very sensitive to overpressurization in compartment 1 and another person might be very sensitive to overpressurization in compartment 6.

 

[LFMarm]

Question:
Would someone surfacing, say, with GF95 after a NDL dive be as aggressive as someone surfacing with GF95 after 2 hours of decompression?

One would think that the latter has some slow compartments heavily loaded, albeit below 95, compared with the former who has virtually no loading of slow compartments?

SurfGF is an aggregate measure across all tissue compartments so it will be hard to tell which of 2 profiles that produce the same SurfGF is more aggressive. It mostly depended on the individual physiology.

On the other hand if you have 2 profiles that produce different SurfGF at the end, the one with the lower SurfGF should be considered less aggressive as it means lower residual inert gas loading. In general all these measures are gross simplifications of the actual human physiology so should be considered directional and not exact.