Shearwater Perdix Tissues Graph

[admikar]

Note that you can also use the Shearwater SurfGF to get a good idea of what the risk is of "getting out the water now." E.g., if your SurfGF is 110%, you might be okay. If your SurfGF is 300%, you are screwed.

- brett

That's an interesting way to think about it.

Personally, I find the SurfGF more useful. That number makes more sense to me than the picture, but I've never thought about it the way you are...

Agree that Surf GF is easier to interpret, but again, it does not tell you which compartent is controling it.
100% SurfGF on fast compartment, for me, is less concerning than same number on mid-compartments.
I use SurfGF and graph to better understand how much risk surfacing would bring.

 

[Wibble]

The Tissue Saturation graph is only for info, for interest if you like. A pretty picture even. It isn't essential and can definitely be ignored.

You'd actually follow other numbers such as the ceiling, surf GF, GF99. Obviously the stop depth and times run the dive. TTS (time to surface) varies according to the mix (PPO2) you're breathing.

 

[Doctor Rig]

Note that you can also use the Shearwater SurfGF to get a good idea of what the risk is of "getting out the water now." E.g., if your SurfGF is 110%, you might be okay. If your SurfGF is 300%, you are screwed.

- brett

Where do I find more info on SurfGF, as I’m not familiar with it?

 

[Wibble]

Where do I find more info on SurfGF, as I’m not familiar with it?

Surface GF and Other Teric Musings - Shearwater Research

Powerful yet Small Imagine having a tool that would give you a numerical percentage value of the decompression stress you would encounter if you were to instantaneously ascend to the surface. Not all dives are […]

www.shearwater.com

 

[Belzelbub]

Where do I find more info on SurfGF, as I’m not familiar with it?

Here, of course. Shearwater also has some info, as the link Wibble posted will give you a bunch of info.

In a nutshell, SurfGF is the GF you could expect if you were to be magically transported to the surface. Not just a direct ascent, but an instantaneous ascent. It’s a pretty useful calculation to gauge risk if you need to omit a stop due to an emergency.

I have SurfGF displayed on my main screen. looking at the tissue graph is a good idea if the SurfGF number is on the high side.

 

[Johnoly]

Where do I find more info on SurfGF, as I’m not familiar with it?

@scubadada has multiple posts that use simple to understand concepts. Maybe he'll chime in.

 

[scubadada]

As per the Teric manual, the SurfGF reflects the GF (GF99), if one instantaneously surfaced. It does not include the ascent nor safety stop/deco stop(s).

I only do no stop dives and about 5% light deco. My use of SurfGF is rather simple, I use it to ensure that my surfacing GF is no higher than the mid-80s. I use it to select the duration of my SS or for padding my deco stop. I now have my surfacing GF from the Shearwater Cloud Desktop for my last 238 dives, 55 +/- 14 (mean +/- std dev) with a range of 13-80. I dive 2 computers, A Shearwater Teric running a GF high of 95 and an Oceanic VT3 running DSAT, around a GF high of 95

DSAT vs GF high 95, examples

I have written previously about my experience diving DSAT and Buhlmann ZH-L16C with a GF high of 95. I have an example of what I have previously reported. This dive is a first dive of the day on the Castor in Boynton Beach. It was relatively deep with a max depth of 107 feet and an avg depth of...

scubaboard.com

 

[boulderjohn]

In a nutshell, SurfGF is the GF you could expect if you were to be magically transported to the surface. Not just a direct ascent, but an instantaneous ascent. It’s a pretty useful calculation to gauge risk if you need to omit a stop due to an emergency.

It will also give you an idea about safety stops on NDL dives.

I recently spent a week of diving in a DM-led group in which my SurfGF was rarely above 35-40 at any point on a dive, and I usually finished the dive below 20. On a couple of dives I finished below 10.. On one dive, I watched it carefully out of curiosity, and it never got above 19. I shook my head in wonder as the group did its safety stops on all those dives. (And, yes, I did those stops with them--why rock the boat?)

 

[Belzelbub]

It will also give you an idea about safety stops on NDL dives.

Correct. I used “stop” without a modifier on purpose to include both deco and safety. But, I should have clarified that it could also be used to extend a safety stop to keep within a personal safety buffer regardless of computer settings.

 

[dmaziuk]

The Tissue Saturation graph is only for info, for interest if you like. A pretty picture even. It isn't essential and can definitely be ignored.

You'd actually follow other numbers such as the ceiling, surf GF, GF99. Obviously the stop depth and times run the dive. TTS (time to surface) varies according to the mix (PPO2) you're breathing.

You're missing @admikar's point though: none of it will tell you which tissues would be controlling if you had to do an emergency ascent that got you over 100%, and thus: whether you'd likely walk away with some oxygen and skin bends, or need a chamber ride.