Meaning of GF settings

Dirk Hohndel dirk at
Sat Jan 5 09:25:40 PST 2013

"Robert C. Helling" <helling at> writes:

> On Jan 5, 2013, at 12:37 PM, Jan Schubert wrote:
> Jan,
>> Oh forgot to put some notes to Dirks question about the "odd shape" of
>> the deco ceiling curve: When calculationg the deco ceiling all the 16
>> tissue compartments has to be taken into account. The deco ceiling is
>> defined by the compartment/tissue having the highest overpressure,
>> called the leading tissue. This leading tissue can (and will!) switch
>> during a dive resulting is such mentionable jumps (ups  and downs) when
>> looking at the smooth deco ceiling curve not based on 3m steps.
> I tend to disagree. At a point in the dive, where the leading
> compartment changes both the old and the new compartment have, quasi
> by definition, the same ceiling (as the total ceiling is the max of
> all compartment ceilings). Thus, when a new compartment becomes the
> lead, there should be no jump in the ceiling (only in the time
> derivative as the ceiling of the new compartment will go up slower, as
> otherwise it could not take over).

That certainly is what I would have expected. As I mentioned elsewhere,
the massive jumps were instead caused by another "add 3m" step in the
ceiling calculation that I had missed when adding the 'smooth' code. But
even with that reduced to 30cm I still get occasional counterintuitive
jumps that have me worried that there may be some instability in the
math involved that I wouldn't expect, looking at the formulas (i.e., I
think there's still a bug hiding somewhere).


More information about the subsurface mailing list