Published sources of ZH-L16C algorithm?

[Rhyno]

By trade I'm in IT and I have a lot of diving related side projects. For a purely theoretical / educational perspective I've been writing my own dive planner. I've successfully implemented ZH-L16A (with a tacked on GF) however many of my computers are currently using C. I'd like to see how my effort varies from the commercial computers I'm using. Does anyone happen to know where I can find the C variant?

English sources are vastly preferred, however any language would be appreciated.

 

[KenGordon]

http://www.ddplan.com/reference/mvalues.pdf

See page 5.

C is just different M values.

 

[Rhyno]

Oh wow, I never expected it to be that simple. Thank you!

 

[Remy B.]

Thanks for the Link Ken, I'm reading the M-value document, and I see very small differences between the B and C models, I ran my Multi-Deco in both modes to a max depth that I want eventually reach. with a GF of 45-75

With what we know so far regarding the avoid stopping deeper, what I see between the B and C is that the C model stop longer deeper ( just a 1min compared to the B model )

and that the B model stops longer ( 1 min longer than the C model ) at intermediate depths

Total run times difference between the two models are only 1 min. ( C model stops 1 min longer at 12m )


But knowing that you are still on-gassing deeper in some compartments, it seems more logical to not stop that long at those depths and it seems as well more logical to stop longer at intermediate depths as you are approaching the surface.

It appear that the differences are not significant, but in this case it looks like in my ignorance that the B model in this case a better decompression approach, and that the C model seems not as much conservative as suggested.

Decompression model: ZHL16-B + GF

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0m
Conservatism = GF 45/75

Dec to 70m (4) Trimix 16/55
Level 70m 30:20 (35) Trimix 16/55
Asc to 54m (37) Trimix 16/55
Asc to 42m (38) Triox 25/25
Stop at 42m 0:30 (39) Triox 25/25
Stop at 36m 2:00 (41) Triox 25/25
Stop at 33m 1:00 (42) Triox 25/25
Stop at 30m 1:00 (43) Triox 25/25
Stop at 27m 3:00 (46) Triox 25/25
Stop at 24m 4:00 (50) Triox 25/25
Stop at 21m 3:00 (53) Nitrox 50
Stop at 18m 5:00 (58) Nitrox 50
Stop at 15m 6:00 (64) Nitrox 50
Stop at 12m 9:00 (73) Nitrox 50
Stop at 9m 11:00 (84) Nitrox 80
Stop at 6m 56:00 (140) Nitrox 80
Surface (141) Nitrox 80 -6m/min ascent.

Decompression model: ZHL16-C + GF

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0m
Conservatism = GF 45/75

Dec to 70m (4) Trimix 16/55
Level 70m 30:20 (35) Trimix 16/55
Asc to 54m (37) Trimix 16/55
Asc to 42m (38) Triox 25/25
Stop at 42m 0:30 (39) Triox 25/25
Stop at 36m 2:00 (41) Triox 25/25
Stop at 33m 1:00 (42) Triox 25/25
Stop at 30m 2:00 (44) Triox 25/25
Stop at 27m 2:00 (46) Triox 25/25
Stop at 24m 4:00 (50) Triox 25/25
Stop at 21m 4:00 (54) Nitrox 50
Stop at 18m 4:00 (58) Nitrox 50
Stop at 15m 6:00 (64) Nitrox 50
Stop at 12m 9:00 (73) Nitrox 50
Stop at 9m 12:00 (85) Nitrox 80
Stop at 6m 56:00 (141) Nitrox 80
Surface (142) Nitrox 80

 

[elmo]

Thanks for the Link Ken, I'm reading the M-value document, and I see very small differences between the B and C models, I ran my Multi-Deco in both modes to a max depth that I want eventually reach. with a GF of 45-75

The B and C models are very close (as your example demonstrates) with C being slightly more conservative. The different sets of Buhlmann coefficients were published back when tables were printed based in the model without adding conservatism (yes, many people dived gf100/100 successfully). Now we use gradient factors, which give you much better control over conservatism than choosing B vs C (which results in just 1min more or less deco for your example dive).
If your aim is to avoid deep stops, don't use such a low gf-low value.

 

[Remy B.]

The GF I chosen is based in my own selection of what I find to be a intermediate area between the two streams of diving approaches and recommendations of the more experienced divers and scientists, as it still a grey area with not yet studies of higher GF and their consequences if any.

Deeper stops were studied and determined that they had a little higher risk of DCS, but there are still divers using that approach successfully, higher GF are been used successfully as well but there have not been studies yet of possible consequences or long term damage to my knowledge, that is why had chosen an intermediate of the both approaches.

I'm moving away from what as per the studies suggest higher risks of DCS but at the same time I'm not going blindly towards suggestions that had not been studied yet.

 

[elmo]

The GF I chosen is based in my own selection of what I find to be a intermediate area between the two streams of diving approaches and recommendations of the more experienced divers and scientists, as it still a grey area with not yet studies of higher GF and their consequences if any.

Deeper stops were studied and determined that they had a little higher risk of DCS, but there are still divers using that approach successfully, higher GF are been used successfully as well but there have not been studies yet of possible consequences or long term damage to my knowledge, that is why had chosen an intermediate of the both approaches.

I'm moving away from what as per the studies suggest higher risks of DCS but at the same time I'm not going blindly towards suggestions that had not been studied yet.

Sorry, I didn't mean to say your choice of gf45/75 was wrong. I think that's a fine choice and I'd happily dive a gf45/75 plan. The point I meant to make was that if the intention was to spend less time at deeper and intermediate stops, increasing gf low will be far more significant than choosing ZHL16-B over ZHL16-C.

 

[Remy B.]

no worries, I didn't take it like you were suggesting I was wrong, just explaining my approach

 

[KenGordon]

If the limiting compartment is one of those with a lower m value in C than B then 45% of that m value will be lower and so the stop will be earlier and/or longer. But the same will go for the last stop, it will be longer.

The whole GF thing a bit of a bodge vs using the correct M values really, the purpose was to introduce conservatism but also to ape the then fashionable deeper stops.