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Use gradient factors in deco calculation

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Usually dive computers show the ceiling in terms of the next deco stop -
and those are in 3m increments. This commit also adds the ability to chose
either the typical 3m increments or the smooth ceiling that the Bühlmann
algorithm actually calculates.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This commit is contained in:
Dirk Hohndel 2013-01-02 23:22:07 -08:00
parent aab67e2a5b
commit 5ba250bd48
5 changed files with 86 additions and 13 deletions
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80
deco.c
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@ -8,6 +8,8 @@
*
* clear_deco() - call to initialize for a new deco calculation
* add_segment(pressure, gasmix) - add 1 second at the given pressure, breathing gasmix
* deco_allowed_depth(tissues_tolerance, surface_pressure, dive, smooth)
* - ceiling based on lead tissue, surface pressure, 3m increments or smooth
*/
#include "dive.h"
@ -24,9 +26,8 @@ struct buehlmann_config {
double gf_high_emergency; //! emergency gf factors
double gf_low_emergency; //! gradient factor low (at bottom/start of deco calculation).
};
struct dive_data
{
struct buehlmann_config buehlmann_config = { 1.0, 1.01, 0.5, 3, 75.0, 35.0, 10.0, 30.0, 95.0, 95.0 };
struct dive_data {
double pressure; //! pesent ambient pressure
double surface; //! pressure at water surface
struct gasmix *gasmix; //! current selected gas
@ -75,14 +76,50 @@ const double buehlmann_He_factor_expositon_one_second[] = {
1.00198406028040E-004, 7.83611475491108E-005, 6.13689891868496E-005, 4.81280465299827E-005};
#define WV_PRESSURE 0.0627 /* water vapor pressure */
#define DIST_FROM_3_MTR 0.28
#define PRESSURE_CHANGE_3M 0.3
#define TOLERANCE 0.02
double tissue_n2_sat[16];
double tissue_he_sat[16];
double tissue_tolerated_ambient_pressure[16];
int ci_pointing_to_guiding_tissue;
double gf_low_position_this_dive;
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 actual_gradient_limit(const struct dive_data *data)
{
double pressure_diff, limit_at_position;
double gf_high = buehlmann_config.gf_high;
double gf_low = buehlmann_config.gf_low;
pressure_diff = data->pressure - data->surface;
if (pressure_diff > TOLERANCE) {
if (pressure_diff < gf_low_position_this_dive)
limit_at_position = gf_high - ((gf_high - gf_low) * pressure_diff / gf_low_position_this_dive);
else
limit_at_position = gf_low;
} else {
limit_at_position = gf_high;
}
return limit_at_position;
}
static double gradient_factor_calculation(const struct dive_data *data)
{
double tissue_inertgas_saturation;
tissue_inertgas_saturation = tissue_n2_sat[ci_pointing_to_guiding_tissue] +
tissue_he_sat[ci_pointing_to_guiding_tissue];
if (tissue_inertgas_saturation < data->pressure)
return 0.0;
else
return (tissue_inertgas_saturation - data->pressure) /
(tissue_inertgas_saturation - tissue_tolerated_ambient_pressure[ci_pointing_to_guiding_tissue]);
}
static double tissue_tolerance_calc(void)
{
@ -104,7 +141,6 @@ static double tissue_tolerance_calc(void)
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);
}
@ -116,7 +152,6 @@ double add_segment(double pressure, struct gasmix *gasmix)
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)
@ -141,3 +176,36 @@ void clear_deco()
}
divetime = 0;
}
unsigned int deco_allowed_depth(double tissues_tolerance, double surface_pressure, struct dive *dive, gboolean smooth)
{
unsigned int depth, multiples_of_3m;
gboolean below_gradient_limit;
double new_gradient_factor;
double pressure_delta = tissues_tolerance - surface_pressure;
struct dive_data mydata;
if (pressure_delta > 0) {
if (!smooth) {
multiples_of_3m = (pressure_delta + DIST_FROM_3_MTR) / 0.3;
depth = 3000 * multiples_of_3m;
} else {
depth = rel_mbar_to_depth(pressure_delta * 1000, dive);
}
} else {
depth = 0;
}
mydata.pressure = surface_pressure + depth / 10000.0;
mydata.surface = surface_pressure;
new_gradient_factor = gradient_factor_calculation(&mydata);
below_gradient_limit = (new_gradient_factor < actual_gradient_limit(&mydata));
while(!below_gradient_limit)
{
mydata.pressure += PRESSURE_CHANGE_3M;
new_gradient_factor = gradient_factor_calculation(&mydata);
below_gradient_limit = (new_gradient_factor < actual_gradient_limit(&mydata));
}
return depth;
}