Dive planner MG, TP and FC

[Willem Ferguson]

Robert,

Can a make a second attempt to make more sense? But this is, I am sure, 
boring to you.

The group that I do deep dives with use a thirds approach: whether you 
dive caves or open water and nothing goes wrong, diver needs a third of 
the back gas remaining at the end of the dive. So, given SAC rate(s) it 
is simple (but sometimes tedious) to calculate the cylinder pressure at 
which ascent starts. But ascent pressure is not merely a third, diver 
and buddy must be able to get to 1st cylinder change depth, so this 
amount is added to the cylinder pressure value of a third. This often 
gives ascent start pressures between 80 and 100 bar. It would be useful 
if this pressure at start of ascent were calculated by Subsurface. The 
reason why this number is useful is of course when one underestimates 
SAC for that particular dive and the bottom time should be shortened 
because of remaining back gas requirement. This number goes on my slate 
every dive, therefore the usefulness. Do I make sense at all this time 
round? Good communication is difficult.
Kind regards,
willem

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