different tissue definiton in OSTC and subsurface

[Jan Schubert]

I just stumbled over the fact that the OSTC seems to use different
definitons for halftime, a and b for N2 and He for the fastest tissue
(#1) then the definitions in subsurface. Some implementations for
Bühlmann different between Tissue 1a and 1b, might be that this might be
a reason, just a guess. Anyway, changig the values to the one used in
the OSTC and also ignoring the precompiled values for 1sec I do not see
much difference in the outcome of the calculated deco for my example (as
in there most likely the slower tissues will lead). Attached is a diff
for this.

Also I've seen the OSTC defining more conservative values for
satmult=0.9 (instead of 1.0) and desatmult=1.1 (1.01) which will result
in much more conservative calculations then we see now so this might
something which I may got wrong.

Just sharing some stuff I found...

Jan

--

diff --git a/deco.c b/deco.c
index 0005ba1..0c9af58 100644
--- a/deco.c
+++ b/deco.c
@@ -35,17 +35,17 @@ struct dive_data {
         struct gasmix *gasmix; //! current selected gas
 };
 
-const double buehlmann_N2_a[] = {1.1696, 1.0, 0.8618, 0.7562,
+const double buehlmann_N2_a[] = {1.2599, 1.0, 0.8618, 0.7562,
                                 0.62, 0.5043, 0.441, 0.4,
                                 0.375, 0.35, 0.3295, 0.3065,
                                 0.2835, 0.261, 0.248, 0.2327};
 
-const double buehlmann_N2_b[] = {0.5578, 0.6514, 0.7222, 0.7825,
+const double buehlmann_N2_b[] = {0.5050, 0.6514, 0.7222, 0.7825,
                                 0.8126, 0.8434, 0.8693, 0.8910,
                                 0.9092, 0.9222, 0.9319, 0.9403,
                                 0.9477, 0.9544, 0.9602, 0.9653};
 
-const double buehlmann_N2_t_halflife[] = {5.0, 8.0, 12.5, 18.5,
+const double buehlmann_N2_t_halflife[] = {4.0, 8.0, 12.5, 18.5,
                                         27.0, 38.3, 54.3, 77.0,
                                         109.0, 146.0, 187.0, 239.0,
                                         305.0, 390.0, 498.0, 635.0};
@@ -56,17 +56,17 @@ const double
buehlmann_N2_factor_expositon_one_second[] = {
        1.05980191127841E-004, 7.91232600646508E-005,
6.17759153688224E-005, 4.83354552742732E-005,
        3.78761777920511E-005, 2.96212356654113E-005,
2.31974277413727E-005, 1.81926738960225E-005};
 
-const double buehlmann_He_a[] = { 1.6189, 1.383 , 1.1919, 1.0458,
+const double buehlmann_He_a[] = { 1.7424, 1.383 , 1.1919, 1.0458,
                                  0.922 , 0.8205, 0.7305, 0.6502,
                                  0.595 , 0.5545, 0.5333, 0.5189,
                                  0.5181, 0.5176, 0.5172, 0.5119};
 
-const double buehlmann_He_b[] = {0.4770, 0.5747, 0.6527, 0.7223,
+const double buehlmann_He_b[] = {0.4245, 0.5747, 0.6527, 0.7223,
                                 0.7582, 0.7957, 0.8279, 0.8553,
                                 0.8757, 0.8903, 0.8997, 0.9073,
                                 0.9122, 0.9171, 0.9217, 0.9267};
 
-const double buehlmann_He_t_halflife[] = {1.88, 3.02, 4.72, 6.99,
+const double buehlmann_He_t_halflife[] = {1.51, 3.02, 4.72, 6.99,
                                          10.21, 14.48, 20.53, 29.11,
                                          41.20, 55.19, 70.69, 90.34,
                                          115.29, 147.42, 188.24, 240.03};