Marine Scientist and Master Instructor
- Reaction score
- U.S. East Coast
- # of dives
- 2500 - 4999
Bingo! Good catch. And the 905mb switchpoint corresponds to 0.893 atm.Today the surface pressure is different but the MOD is the same, so I thought that likely SP is taking into account the fact that I am at altitude class C1 and according to their G2 manual (pg 53) the switch point from C0 to C1 is 905 mbar, so I think it doesnt take the surface P into account when giving the MOD, but rather just a fixed value of 0.92 - which makes sense otherwise your MOD will be changing slightly all the time.
Thus: (1.4/0.32 -0.893)*10=34.82m. You got 34.6.
You are hung up on surface pressure being 0.92 atm (932mb), but I see no justification for that other than getting the answer you want...which could also be done (by SP) by increasing the FO2.
If SP is so smart, they will also not accept "salt" for a dive at C1 altitude. So 10m/atm ought to be 10.3 or 10.4, depending on your druthers.