diff options
Diffstat (limited to 'core/dive.c')
| -rw-r--r-- | core/dive.c | 26 |
1 files changed, 18 insertions, 8 deletions
diff --git a/core/dive.c b/core/dive.c index 6bed5966a..49a468e5a 100644 --- a/core/dive.c +++ b/core/dive.c @@ -38,6 +38,8 @@ const char *divemode_text_ui[] = { // For writing/reading files. const char *divemode_text[] = {"OC", "CCR", "PSCR", "Freedive"}; +static int calculate_depth_to_mbar(int depth, pressure_t surface_pressure, int salinity); + /* * Adding a cylinder pressure sample field is not quite as trivial as it * perhaps should be. @@ -3688,10 +3690,20 @@ int get_surface_pressure_in_mbar(const struct dive *dive, bool non_null) return mbar; } +/* This returns the conversion factor that you need to multiply + * a (relative) depth in mm to obtain a (relative) pressure in mbar. + * As everywhere in Subsurface, the expected unit of a salinity is + * g/10l such that sea water has a salinity of 10300 + */ +static double salinity_to_specific_weight(int salinity) +{ + return salinity * 0.981 / 100000.0; +} + /* Pa = N/m^2 - so we determine the weight (in N) of the mass of 10m * of water (and use standard salt water at 1.03kg per liter if we don't know salinity) * and add that to the surface pressure (or to 1013 if that's unknown) */ -int calculate_depth_to_mbar(int depth, pressure_t surface_pressure, int salinity) +static int calculate_depth_to_mbar(int depth, pressure_t surface_pressure, int salinity) { double specific_weight; int mbar = surface_pressure.mbar; @@ -3702,8 +3714,8 @@ int calculate_depth_to_mbar(int depth, pressure_t surface_pressure, int salinity salinity = SEAWATER_SALINITY; if (salinity < 500) salinity += FRESHWATER_SALINITY; - specific_weight = salinity / 10000.0 * 0.981; - mbar += lrint(depth / 10.0 * specific_weight); + specific_weight = salinity_to_specific_weight(salinity); + mbar += lrint(depth * specific_weight); return mbar; } @@ -3728,13 +3740,11 @@ double depth_to_atm(int depth, const struct dive *dive) * take care of this, but the Uemis we support natively */ int rel_mbar_to_depth(int mbar, const struct dive *dive) { - int cm; - double specific_weight = SEAWATER_SALINITY * 0.981 / 10000.0; + double specific_weight = salinity_to_specific_weight(SEAWATER_SALINITY); if (dive->dc.salinity) - specific_weight = dive->dc.salinity / 10000.0 * 0.981; + specific_weight = salinity_to_specific_weight(dive->dc.salinity); /* whole mbar gives us cm precision */ - cm = (int)lrint(mbar / specific_weight); - return cm * 10; + return (int)lrint(mbar / specific_weight); } int mbar_to_depth(int mbar, const struct dive *dive) |