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/* calculate deco values
* based on Bühlmann ZHL-16b
* based on an implemention by heinrichs weikamp for the DR5
* the original file doesn't carry a license and is used here with
* the permission of Matthias Heinrichs
*
* The implementation below is (C) Dirk Hohndel 2012 and released under the GPLv2
*
* clear_deco() - call to initialize for a new deco calculation
* add_segment(pressure, gasmix) - add 1 second at the given pressure, breathing gasmix
*/
#include "dive.h"
//! Option structure for Buehlmann decompression.
struct buehlmann_config {
double satmult; //! safety at inert gas accumulation as percentage of effect (more than 100).
double desatmult; //! safety at inert gas depletion as percentage of effect (less than 100).
double safety_dist_deco_stop;//! assumed distance to official decompression where decompression takes places.
int last_deco_stop_in_mtr; //! depth of last_deco_stop.
double gf_high; //! gradient factor high (at surface).
double gf_low; //! gradient factor low (at bottom/start of deco calculation).
double gf_low_position_min; //! gf_low_position below surface_min_shallow.
double gf_low_position_max; //! gf_low_position below surface_max_depth.
double gf_high_emergency; //! emergency gf factors
double gf_low_emergency; //! gradient factor low (at bottom/start of deco calculation).
};
struct dive_data
{
double pressure; //! pesent ambient pressure
double surface; //! pressure at water surface
struct gasmix *gasmix; //! current selected gas
};
const double buehlmann_N2_a[] = {1.1696, 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,
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,
27.0, 38.3, 54.3, 77.0,
109.0, 146.0, 187.0, 239.0,
305.0, 390.0, 498.0, 635.0};
const double buehlmann_N2_factor_expositon_one_second[] = {
2.30782347297664E-003, 1.44301447809736E-003, 9.23769302935806E-004, 6.24261986779007E-004,
4.27777107246730E-004, 3.01585140931371E-004, 2.12729727268379E-004, 1.50020603047807E-004,
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,
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,
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,
10.21, 14.48, 20.53, 29.11,
41.20, 55.19, 70.69, 90.34,
115.29, 147.42, 188.24, 240.03};
const double buehlmann_He_factor_expositon_one_second[] = {
6.12608039419837E-003, 3.81800836683133E-003, 2.44456078654209E-003, 1.65134647076792E-003,
1.13084424730725E-003, 7.97503165599123E-004, 5.62552521860549E-004, 3.96776399429366E-004,
2.80360036664540E-004, 2.09299583354805E-004, 1.63410794820518E-004, 1.27869320250551E-004,
1.00198406028040E-004, 7.83611475491108E-005, 6.13689891868496E-005, 4.81280465299827E-005};
#define WV_PRESSURE 0.0627 /* water vapor pressure */
double tissue_n2_sat[16];
double tissue_he_sat[16];
double tissue_tolerated_ambient_pressure[16];
int ci_pointing_to_guiding_tissue;
int divetime;
struct buehlmann_config buehlmann_config = { 1.0, 1.01, 0.5, 3, 95.0, 95.0, 10.0, 30.0, 95.0, 95.0 };
static double tissue_tolerance_calc(void)
{
int ci = -1;
double tissue_inertgas_saturation, buehlmann_inertgas_a, buehlmann_inertgas_b;
double ret_tolerance_limit_ambient_pressure = -1.0;
for (ci = 0; ci < 16; ci++)
{
tissue_inertgas_saturation = tissue_n2_sat[ci] + tissue_he_sat[ci];
buehlmann_inertgas_a = ((buehlmann_N2_a[ci] * tissue_n2_sat[ci]) + (buehlmann_He_a[ci] * tissue_he_sat[ci])) / tissue_inertgas_saturation;
buehlmann_inertgas_b = ((buehlmann_N2_b[ci] * tissue_n2_sat[ci]) + (buehlmann_He_b[ci] * tissue_he_sat[ci])) / tissue_inertgas_saturation;
tissue_tolerated_ambient_pressure[ci] = (tissue_inertgas_saturation - buehlmann_inertgas_a) * buehlmann_inertgas_b;
if (tissue_tolerated_ambient_pressure[ci] > ret_tolerance_limit_ambient_pressure)
{
ci_pointing_to_guiding_tissue = ci;
ret_tolerance_limit_ambient_pressure = tissue_tolerated_ambient_pressure[ci];
}
}
printf("%d:%02u %lf\n",FRACTION(divetime, 60), ret_tolerance_limit_ambient_pressure);
return (ret_tolerance_limit_ambient_pressure);
}
/* add a second at the given pressure and gas to the deco calculation */
double add_segment(double pressure, struct gasmix *gasmix)
{
int ci;
double ppn2 = (pressure - WV_PRESSURE) * (1000 - gasmix->o2.permille - gasmix->he.permille) / 1000.0;
double pphe = (pressure - WV_PRESSURE) * gasmix->he.permille / 1000.0;
divetime++;
printf("%2d:%02u N2 %2.3lf He %2.3lf",FRACTION(divetime, 60), ppn2, pphe);
/* right now we just do OC */
for (ci = 0; ci < 16; ci++) {
if (ppn2 - tissue_n2_sat[ci] > 0)
tissue_n2_sat[ci] += buehlmann_config.satmult * (ppn2 - tissue_n2_sat[ci]) * buehlmann_N2_factor_expositon_one_second[ci];
else
tissue_n2_sat[ci] += buehlmann_config.desatmult * (ppn2 - tissue_n2_sat[ci]) * buehlmann_N2_factor_expositon_one_second[ci];
if (pphe - tissue_he_sat[ci] > 0)
tissue_he_sat[ci] += buehlmann_config.satmult * (pphe - tissue_he_sat[ci]) * buehlmann_He_factor_expositon_one_second[ci];
else
tissue_he_sat[ci] += buehlmann_config.desatmult * (pphe - tissue_he_sat[ci]) * buehlmann_He_factor_expositon_one_second[ci];
}
return tissue_tolerance_calc();
}
void clear_deco()
{
int ci;
for (ci = 0; ci < 16; ci++) {
tissue_n2_sat[ci] = 0.0;
tissue_he_sat[ci] = 0.0;
tissue_tolerated_ambient_pressure[ci] = 0.0;
}
divetime = 0;
}
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