+}
+
+
+void FGAtmosphere::Calculate(void)
+{
+ //see reference [1]
+
+ float slope,reftemp,refpress,refdens;
+ int i=0;
+ float htab[]={0,36089,82020,154198,173882,259183,295272,344484}; //ft.
+
+ if (h <= htab[0]) {
+ h=0;
+ } else if (h >= htab[7]){
+ i = 7;
+ h = htab[7];
+ } else {
+ while (htab[i+1] < h) {
+ i++;
+ }
+ }
+
+ switch(i) {
+ case 0: // sea level
+ slope = -0.0035662; // R/ft.
+ reftemp = 518.688; // R
+ refpress = 2116.17; // psf
+ refdens = 0.0023765; // slugs/cubic ft.
+ break;
+ case 1: // 36089 ft.
+ slope = 0;
+ reftemp = 389.988;
+ refpress = 474.1;
+ refdens = 0.0007078;
+ break;
+ case 2: // 82020 ft.
+ slope = 0.00164594;
+ reftemp = 389.988;
+ refpress = 52.7838;
+ refdens = 7.8849E-5;
+ break;
+ case 3: // 154198 ft.
+ slope = 0;
+ reftemp = 508.788;
+ refpress = 2.62274;
+ refdens = 3.01379E-6;
+ break;
+ case 4: // 173882 ft.
+ slope = -0.00246891;
+ reftemp = 508.788;
+ refpress = 1.28428;
+ refdens = 1.47035e-06;
+ break;
+ case 5: // 259183 ft.
+ slope = 0;
+ reftemp = 298.188;
+ refpress = 0.0222008;
+ refdens = 4.33396e-08;
+ break;
+ case 6: // 295272 ft.
+ slope = 0.00219459;
+ reftemp = 298.188;
+ refpress = 0.00215742;
+ refdens = 4.21368e-09;
+ break;
+ case 7: // 344484 ft.
+ slope = 0;
+ reftemp = 406.188;
+ refpress = 0.000153755;
+ refdens = 2.20384e-10;
+ break;
+ }
+
+
+ if (slope == 0) {
+ temperature = reftemp;
+ pressure = refpress*exp(-GRAVITY/(reftemp*Reng)*(h-htab[i]));
+ density = refdens*exp(-GRAVITY/(reftemp*Reng)*(h-htab[i]));
+ } else {
+ temperature = reftemp+slope*(h-htab[i]);
+ pressure = refpress*pow(temperature/reftemp,-GRAVITY/(slope*Reng));
+ density = refdens*pow(temperature/reftemp,-(GRAVITY/(slope*Reng)+1));
+ }
+
+ soundspeed = sqrt(SHRATIO*Reng*temperature);
+
+}
+
+
+float FGAtmosphere::GetTemperature(float altitude)
+{
+ if (altitude != h) {
+ h = altitude;
+ Calculate();
+ }
+ return temperature;
+}
+
+
+float FGAtmosphere::GetPressure(float altitude)
+{
+ if (altitude != h) {
+ h = altitude;
+ Calculate();
+ }
+
+ return pressure;
+}
+
+float FGAtmosphere::GetDensity(float altitude)
+{
+ if (altitude != h) {
+ h = altitude;
+ Calculate();
+ }
+
+ return density;
+}
+
+
+float FGAtmosphere::GetSoundSpeed(float altitude)
+{
+ if (altitude != h) {
+ h = altitude;
+ Calculate();
+ }