#include <simgear/constants.h>
#include <simgear/debug/logstream.hxx>
#include <simgear/math/interpolater.hxx>
+#include <simgear/props/props.hxx>
#include <simgear/environment/visual_enviro.hxx>
#include <Main/fg_props.hxx>
+
#include "environment.hxx"
// Atmosphere model.
////////////////////////////////////////////////////////////////////////
-// Copied from YASim Atmosphere.cxx, with m converted to ft, degK
-// converted to degC, Pa converted to inHG, and kg/m^3 converted to
-// slug/ft^3; they were then converted to deltas from the sea-level
-// defaults (approx. 15degC, 29.92inHG, and 0.00237slugs/ft^3).
-
-// Original comment from YASim:
-
-// Copied from McCormick, who got it from "The ARDC Model Atmosphere"
-// Note that there's an error in the text in the first entry,
-// McCormick lists 299.16/101325/1.22500, but those don't agree with
-// R=287. I chose to correct the temperature to 288.20, since 79F is
-// pretty hot for a "standard" atmosphere.
+// Calculated based on the ISA standard day, as found at e.g.
+// http://www.av8n.com/physics/altimetry.htm
-// Elevation (ft), temperature factor (degK), pressure factor (inHG)
+// Each line of data has 3 elements:
+// Elevation (ft),
+// temperature factor (dimensionless ratio of absolute temp),
+// pressure factor (dimensionless ratio)
static double atmosphere_data[][3] = {
- { 0.00, 1.00, 1.000 },
- { 2952.76, 0.98, 0.898 },
- { 5905.51, 0.96, 0.804 },
- { 8858.27, 0.94, 0.719 },
- { 11811.02, 0.92, 0.641 },
- { 14763.78, 0.90, 0.570 },
- { 17716.54, 0.88, 0.506 },
- { 20669.29, 0.86, 0.447 },
- { 23622.05, 0.84, 0.394 },
- { 26574.80, 0.82, 0.347 },
- { 29527.56, 0.80, 0.304 },
- { 32480.31, 0.78, 0.266 },
- { 35433.07, 0.76, 0.231 },
- { 38385.83, 0.75, 0.201 },
- { 41338.58, 0.75, 0.174 },
- { 44291.34, 0.75, 0.151 },
- { 47244.09, 0.75, 0.131 },
- { 50196.85, 0.75, 0.114 },
- { 53149.61, 0.75, 0.099 },
- { 56102.36, 0.75, 0.086 },
- { 59055.12, 0.75, 0.075 },
- { 62007.87, 0.75, 0.065 },
+ { -3000.00, 1.021, 1.1133 },
+ { 0.00, 1.000, 1.0000 },
+ { 2952.76, 0.980, 0.8978 },
+ { 5905.51, 0.959, 0.8042 },
+ { 8858.27, 0.939, 0.7187 },
+ { 11811.02, 0.919, 0.6407 },
+ { 14763.78, 0.898, 0.5697 },
+ { 17716.54, 0.878, 0.5052 },
+ { 20669.29, 0.858, 0.4468 },
+ { 23622.05, 0.838, 0.3940 },
+ { 26574.80, 0.817, 0.3463 },
+ { 29527.56, 0.797, 0.3034 },
+ { 32480.31, 0.777, 0.2649 },
+ { 35433.07, 0.756, 0.2305 },
+ { 38385.83, 0.752, 0.2000 },
+ { 41338.58, 0.752, 0.1736 },
+ { 44291.34, 0.752, 0.1506 },
+ { 47244.09, 0.752, 0.1307 },
+ { 50196.85, 0.752, 0.1134 },
+ { 53149.61, 0.752, 0.0984 },
+ { 56102.36, 0.752, 0.0854 },
+ { 59055.12, 0.752, 0.0741 },
+ { 62007.87, 0.752, 0.0643 },
+ { 65000.00, 0.752, 0.0557 },
+ { 68000.00, 0.754, 0.0482 },
+ { 71000.00, 0.758, 0.0418 },
+ { 74000.00, 0.761, 0.0362 },
+ { 77000.00, 0.764, 0.0314 },
+ { 80000.00, 0.767, 0.0273 },
+ { 83000.00, 0.770, 0.0237 },
+ { 86000.00, 0.773, 0.0206 },
+ { 89000.00, 0.777, 0.0179 },
+ { 92000.00, 0.780, 0.0156 },
+ { 95000.00, 0.783, 0.0135 },
+ { 98000.00, 0.786, 0.0118 },
+ { 101000.00, 0.789, 0.0103 },
{ -1, -1, -1 }
};
{
// If we're in the stratosphere, leave sea-level temp alone
if (elevation_ft < 38000) {
- temperature_sea_level_degc =
- (temperature_degc + 273.15)
- /_temperature_degc_table->interpolate(elevation_ft)
+ temperature_sea_level_degc = (temperature_degc + 273.15)
+ / _temperature_degc_table->interpolate(elevation_ft)
- 273.15;
}
}
FGEnvironment::_recalc_alt_temperature ()
{
if (elevation_ft < 38000) {
- temperature_degc =
- (temperature_sea_level_degc + 273.15) *
- _temperature_degc_table->interpolate(elevation_ft) - 273.15;
+ temperature_degc = (temperature_sea_level_degc + 273.15) *
+ _temperature_degc_table->interpolate(elevation_ft) - 273.15;
} else {
temperature_degc = -56.49; // Stratosphere is constant
}
FGEnvironment::_recalc_density_tropo_avg_kgm3 ()
{
double pressure_mb = pressure_inhg * 33.86;
- double vaporpressure = 6.11 * pow ( 10, ((7.5 * dewpoint_degc) /( 237.7 + dewpoint_degc)));
+ double vaporpressure = 6.11 * pow(10.0, ((7.5 * dewpoint_degc) / (237.7 + dewpoint_degc)));
double virtual_temp = (temperature_degc + 273.15) / (1 - 0.379 * (vaporpressure/pressure_mb));
- double density_half = (100* pressure_mb * exp (-altitude_half_to_sun_m / 8000)) / (287.05 * virtual_temp);
- double density_tropo = (100* pressure_mb * exp ((-1 * altitude_tropo_top_m) / 8000)) /( 287.05 * virtual_temp);
+ double density_half = (100 * pressure_mb * exp(-altitude_half_to_sun_m / 8000))
+ / (287.05 * virtual_temp);
+ double density_tropo = (100 * pressure_mb * exp((-1 * altitude_tropo_top_m) / 8000))
+ / ( 287.05 * virtual_temp);
density_tropo_avg_kgm3 = ((density_slugft3 * 515.379) + density_half + density_tropo) / 3;
}
void
FGEnvironment::_recalc_relative_humidity ()
{
- double vaporpressure = 6.11 * pow ( 10, ((7.5 * dewpoint_degc) /( 237.7 + dewpoint_degc)));
- double sat_vaporpressure = 6.11 * pow ( 10, ((7.5 * temperature_degc) /( 237.7 + temperature_degc)) );
- relative_humidity = 100 *vaporpressure / sat_vaporpressure ;
+ double vaporpressure = 6.11 * pow(10.0, ((7.5 * dewpoint_degc) / ( 237.7 + dewpoint_degc)));
+ double sat_vaporpressure = 6.11 * pow(10.0, ((7.5 * temperature_degc)
+ / ( 237.7 + temperature_degc)) );
+ relative_humidity = 100 * vaporpressure / sat_vaporpressure ;
}
projects / flightgear.git / blobdiff