diff options
| -rw-r--r-- | dive.c | 31 | ||||
| -rw-r--r-- | dive.h | 6 | ||||
| -rw-r--r-- | divelist.c | 13 | ||||
| -rw-r--r-- | profile.c | 34 | ||||
| -rw-r--r-- | statistics.c | 10 |
5 files changed, 58 insertions, 36 deletions
@@ -286,6 +286,29 @@ static void update_min_max_temperatures(struct dive *dive, temperature_t tempera } } +/* + * At high pressures air becomes less compressible, and + * does not follow the ideal gas law any more. + * + * This tries to correct for that, becoming the same + * as to_ATM() at lower pressures. + * + * THIS IS A ROUGH APPROXIMATION! The real numbers will + * depend on the exact gas mix and temperature. + */ +double surface_volume_multiplier(pressure_t pressure) +{ + double bar = pressure.mbar / 1000.0; + + if (bar > 200) + bar = 0.00038*bar*bar + 0.51629*bar + 81.542; + return bar_to_atm(bar); +} + +int gas_volume(cylinder_t *cyl, pressure_t p) +{ + return cyl->type.size.mliter * surface_volume_multiplier(p); +} /* * If the cylinder tank pressures are within half a bar @@ -338,7 +361,7 @@ static void match_standard_cylinder(cylinder_type_t *type) return; cuft = ml_to_cuft(type->size.mliter); - cuft *= to_ATM(type->workingpressure); + cuft *= surface_volume_multiplier(type->workingpressure); psi = to_PSI(type->workingpressure); switch (psi) { @@ -381,7 +404,7 @@ static void match_standard_cylinder(cylinder_type_t *type) */ static void sanitize_cylinder_type(cylinder_type_t *type) { - double volume_of_air, atm, volume; + double volume_of_air, volume; /* If we have no working pressure, it had *better* be just a physical size! */ if (!type->workingpressure.mbar) @@ -394,8 +417,8 @@ static void sanitize_cylinder_type(cylinder_type_t *type) if (xml_parsing_units.volume == CUFT) { /* confusing - we don't really start from ml but millicuft !*/ volume_of_air = cuft_to_l(type->size.mliter); - atm = to_ATM(type->workingpressure); /* working pressure in atm */ - volume = volume_of_air / atm; /* milliliters at 1 atm: "true size" */ + /* milliliters at 1 atm: "true size" */ + volume = volume_of_air / surface_volume_multiplier(type->workingpressure); type->size.mliter = volume + 0.5; } @@ -203,10 +203,8 @@ static inline double bar_to_atm(double bar) return bar / SURFACE_PRESSURE * 1000; } -static inline double to_ATM(pressure_t pressure) -{ - return pressure.mbar / (double) SURFACE_PRESSURE; -} +/* Volume in mliter of a cylinder at pressure 'p' */ +extern int gas_volume(cylinder_t *cyl, pressure_t p); static inline int mbar_to_PSI(int mbar) { diff --git a/divelist.c b/divelist.c index 952b03bb2..1c020afe4 100644 --- a/divelist.c +++ b/divelist.c @@ -697,26 +697,19 @@ static int calculate_otu(struct dive *dive) */ static double calculate_airuse(struct dive *dive) { - double airuse = 0; + int airuse = 0; int i; for (i = 0; i < MAX_CYLINDERS; i++) { pressure_t start, end; cylinder_t *cyl = dive->cylinder + i; - int size = cyl->type.size.mliter; - double kilo_atm; - - if (!size) - continue; start = cyl->start.mbar ? cyl->start : cyl->sample_start; end = cyl->end.mbar ? cyl->end : cyl->sample_end; - kilo_atm = (to_ATM(start) - to_ATM(end)) / 1000.0; - /* Liters of air at 1 atm == milliliters at 1k atm*/ - airuse += kilo_atm * size; + airuse += gas_volume(cyl, start) - gas_volume(cyl, end); } - return airuse; + return airuse / 1000.0; } /* this only uses the first divecomputer to calculate the SAC rate */ @@ -1011,32 +1011,40 @@ static void set_sac_color(struct graphics_context *gc, int sac, int avg_sac) } } -static double get_local_sac(struct plot_data *entry1, struct plot_data *entry2, struct dive *dive) +/* Get local sac-rate (in ml/min) between entry1 and entry2 */ +static int get_local_sac(struct plot_data *entry1, struct plot_data *entry2, struct dive *dive) { int index = entry1->cylinderindex; - int delta_time = entry2->sec - entry1->sec; - double depth; - long delta_pressure = GET_PRESSURE(entry1) - GET_PRESSURE(entry2); - long mliter; + cylinder_t *cyl; + int duration = entry2->sec - entry1->sec; + int depth, airuse; + pressure_t a, b; + double atm; if (entry2->cylinderindex != index) return 0; - if (delta_pressure <= 0) + if (duration <= 0) return 0; - if (delta_time <= 0) + a.mbar = GET_PRESSURE(entry1); + b.mbar = GET_PRESSURE(entry2); + if (!a.mbar || !b.mbar) return 0; - depth = (entry1->depth + entry2->depth) / 2.0; - mliter = dive->cylinder[index].type.size.mliter; + /* Mean pressure in ATM */ + depth = (entry1->depth + entry2->depth) / 2; + atm = (double) depth_to_mbar(depth, dive) / SURFACE_PRESSURE; - return delta_pressure * mliter / - (delta_time / 60.0) / - depth_to_mbar(depth, dive); + cyl = dive->cylinder + index; + + airuse = gas_volume(cyl, a) - gas_volume(cyl, b); + + /* milliliters per minute */ + return airuse / atm * 60 / duration; } /* calculate the current SAC in ml/min and convert to int */ #define GET_LOCAL_SAC(_entry1, _entry2, _dive) \ - (int) get_local_sac(_entry1, _entry2, _dive) + get_local_sac(_entry1, _entry2, _dive) #define SAC_WINDOW 45 /* sliding window in seconds for current SAC calculation */ diff --git a/statistics.c b/statistics.c index 9cbfcc72f..b6b618fbd 100644 --- a/statistics.c +++ b/statistics.c @@ -604,10 +604,10 @@ static void show_single_dive_stats(struct dive *dive) /* for the O2/He readings just create a list of them */ for (idx = 0; idx < MAX_CYLINDERS; idx++) { cylinder_t *cyl = &dive->cylinder[idx]; - unsigned int start, end; + pressure_t start, end; - start = cyl->start.mbar ? : cyl->sample_start.mbar; - end = cyl->end.mbar ? : cyl->sample_end.mbar; + start = cyl->start.mbar ? cyl->start : cyl->sample_start; + end = cyl->end.mbar ?cyl->sample_end : cyl->sample_end; if (!cylinder_none(cyl)) { /* 0% O2 strangely means air, so 21% - I don't like that at all */ int o2 = cyl->gasmix.o2.permille ? : O2_IN_AIR; @@ -621,8 +621,8 @@ static void show_single_dive_stats(struct dive *dive) } /* and if we have size, start and end pressure, we can * calculate the total gas used */ - if (cyl->type.size.mliter && start && end) - gas_used += cyl->type.size.mliter / 1000.0 * (start - end); + if (start.mbar && end.mbar) + gas_used += gas_volume(cyl, start) - gas_volume(cyl, end); } set_label(single_w.o2he, buf); if (gas_used) { |