Planner: Multiple Deco calculations ?

Dirk Hohndel dirk at hohndel.org
Thu Aug 28 07:38:37 PDT 2014


On Thu, Aug 28, 2014 at 04:30:31PM +0200, Guillaume Gardet wrote:
> 
> For Bühlmann there are multiple models :
> * number of tissue compartments (8, 12 or 16)
> * A/B/C variants (at least for ZHL-16): A is theoretical only, B is for tables generation and C is for dive computer (more conservative).
> 
> So, we could implement those variants.

The biggest challenge here is "who would implement this".
We have learned that the discrete implementation of these models is rather
tricky (as a divelog we only get the samples at the sample rate the dive
computer returns to us). And because of that, even if we know exactly
which model a dive computer is designed to implement, we still usually
don't match the deco data the dive computer shows, as it has access to the
continuous depth information. Additionally many divecomputers have rather
under-powered CPUs (to say the least) and they are taking serious
shortcuts when calculating the compartment values - which also leads to
different results.

Long story short: it's not clear to me if there is value in implementing
other variations of the Buhlmann algorithm - it's unlikely we'll ever
perfectly "match" any dive computer you are diving.

I'd be more interested in a VPM implementation (that is reasonably well
documented). We had a GSOC proposal to do just that and decided not to
accept it but it's still something that we are open to if there's a
developer with the necessary math / physics background willing to tackle
the problem.

/D


More information about the subsurface mailing list