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H2Ocaver wrote:
>2)Bottom time starts when you hit the bottom and ends when you leave the
bottom PERIOD.
Pretty certain ("PERIOD")??? But wrong! Even your most basic PADI course
instructs that bottom time is the time you leave the surface to the time
you start an uninterrupted ascent to your first stop. If it becomes
interrupted, then it becomes multi-level. Following generally recognized
decompression theories (e.g. Buhlmann, Workman - the basis for many tables
and computer programs) you will find their guidelines for constructing dive
tables define bottom time in the same way. They also define an ascent rate
which figures into the inert gas loading for computing an empirical
decompression. It depends on how you wish to solve the differential
equations (Workman has solved for a changing gradient on descent, but I
believe the tables based on his work lump descent time with bottom time as
well). Sure, there may be some statistical methods that may wish to define
bottom time differently, but it would be interesting to understand how to
account for descent time without solving or accounting for incremental gas
loading during the descent or lumping it into the time on the bottom (for
simplicity and margin). Case in point: On a 400ft dive, you take 4 minutes
to make your descent, and then do a 20 minute time on the bottom. Are you
saying the 4 minutes should be ignored and only the 20 minutes considerd?
Not in my program. Gas loading is a function of a gradient and time of
exposure, regardless of the type of gas. Hey I'm open for hearing relevant
information about new and improved decompression theories.
Take care,
Doug
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