Gradient Factor Presets by Manufacturer/Computer

[tursiops]

I'd find it easier to comment on your sorting if I understood your objective.

 

[CandiveOz]

So I sorted the data first by Rec/Tec and then by GF-hi followed by GF-lo which is more logical compared to my initial sort. I also colour coded similar presets between manufacturers. It looks like Garmin just copied Shearwater.

 

[CandiveOz]

I'd find it easier to comment on your sorting if I understood your objective.

1. The first objective is to compile a list of all GF presets offered by DC manufacturers and sort them in a meaningful way.
2. The second objective is to find commonality within the list (coloured areas)
3. The third objective is to initiate a discussion regarding the presets.

With regards to the third objective some questions may be as follows;

1. Do the presets look reasonable? Are they useful for to most divers?
2. Is a GF spread of 10 (eg. 70/80) really big enough or is it just a marketing gimmick?
3. Likewise, is a GF spread of 60 or 69 (eg. 20/89) too much?
4. Is 40/85 more conservative than 85/85? If so, then what about 30/85?
   
5. If recreational diving is mostly NDL, why have a lower GF-lo than GF-hi if it rarely if ever comes into play? Why make something simple complex? Just keep it flat (eg. 80/80).
6. With the presets listed above, would you refrain from using some of them (eg. 25/40)?
7. Should manufacturers offer inverse settings (eg. 90/70)?
8. Should the industry standardise presets to minimise market confusion but offer custom settings as well?
9. If you were responsible for specifying 3-6 presets for a new computer, what would they be?

 

[dmaziuk]

Is a GF spread of 10 (eg. 70/80) really big enough or is it just a marketing gimmick?
Likewise, is a GF spread of 60 or 69 (eg. 20/89) too much?

We just did this in the "gf lo ndl" thread: the algorithm is non-continuous when you cross from no-stop into deco, one way around it is to limit what you call the "spread" in the "recreational" preset. I.e. in rec. mode 10 is just as good as 0, if you recall that thread 80 (10/90) was shown to be too much, and you'd need to run the numbers to see how 40-50 stacks up.

On planned deco dives it's up to you whether you want to add conservatism evenly to the "stock" M-values (low spread), or give your faster tissues a relatively greater safety margin. That said, I'd come up with some kind of "overall" measure, like integral super-saturation maybe, and look at a few different profiles: I wouldn't be surprised if the same spread works out differently on short and deep wreck dive vs long and shallow cave dive.

 

[CandiveOz]

@dmaziuk I like your suggestion of developing an "overall" measure but I don't think I have the technical expertise to develop one. Perhaps you can expand on your idea of "intergral super-saturation." An example would be most helpful.

 

[dmaziuk]

Use the Search, Luke: NEDU Study

 

[CandiveOz]

Thanks for the link and I will certainly look up the gf lo NDL thread.

 

[CandiveOz]

When we discuss gradient factors we tend to define GF-hi in terms of risk, either liberal settings or conservative settings. As for GF-lo, since it dictates the first deco stop we define it in terms of depth, shallow, intermediate or deep. I created a table that defines the ranges for the different settings and I and I sorted the presets in terms of risk and depth. Let me know if you agree with my ranges and or suggest other terminology we can use to define these ranges.

 

[dmaziuk]

You could consider using the delta or spread instead of absolute GF Lo value. The rationale would be that the base conservatism (your "in terms of risk") level is not the GF Hi but rather the GF slope at GF Hi = GF Lo. You really should read the original paper: https://www.shearwater.com/wp-content/uploads/2012/08/Deep-Stops.pdf

 

[KenGordon]

When we discuss gradient factors we tend to define GF-hi in terms of risk, either liberal settings or conservative settings. As for GF-lo, since it dictates the first deco stop we define it in terms of depth, shallow, intermediate or deep. I created a table that defines the ranges for the different settings and I and I sorted the presets in terms of risk and depth. Let me know if you agree with my ranges and or suggest other terminology we can use to define these ranges.

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I think you should not attach words like “aggressive” or “conservative” to dive plans, and especially to settings. Those words carry meaning to casual readers which isn’t actually there. You can get bent on a conservative plan, it is a matter of probability. Which probability counts as “conservative”?

One of the issues with ZHL16C is that it doesn’t work the same of all depths. So “conservative” on a 20m dive might be “aggressive” on a 100m dive. It is too complicated yo boil down it down this way, especially with the GF twists.