Opt: Option to query all altitude dependent values in one ...

This avoids duplicate GetTemperature()/GetPressure() calls.

Author: Chris Birkhold

src/models/FGAtmosphere.cpp

@@ -137,6 +137,16 @@ double FGAtmosphere::ValidateTemperature(double t, const string& msg, bool quiet
 
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
+void FGAtmosphere::GetAltitudeDependentValues(AltitudeDependentValues& values, double altitude) const
+{
+  values.Temperature = GetTemperature(altitude);
+  values.Pressure = GetPressure(altitude);
+  values.Density = (values.Pressure / (Reng * values.Temperature));
+  values.SoundSpeed = sqrt(SHRatio * Reng * values.Temperature);
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
 void FGAtmosphere::Calculate(double altitude)
 {
   FGPropertyNode* node = PropertyManager->GetNode();

src/models/FGAtmosphere.h

@@ -82,6 +82,13 @@ class JSBSIM_API FGAtmosphere : public FGModel {
   /// Enums for specifying pressure units.
   enum ePressure {eNoPressUnit=0, ePSF, eMillibars, ePascals, eInchesHg};
 
+  typedef struct AltitudeDependentValues {
+    double Temperature = 0.0;
+    double Pressure = 0.0;
+    double Density = 0.0;
+    double SoundSpeed = 0.0;
+  } AltitudeDependentValues;
+
   /// Constructor
   FGAtmosphere(FGFDMExec*);
 
@@ -206,6 +213,8 @@ class JSBSIM_API FGAtmosphere : public FGModel {
 
   virtual double GetPressureAltitude() const {return PressureAltitude;}
 
+  virtual void GetAltitudeDependentValues(AltitudeDependentValues& values, double altitude) const;
+
   struct Inputs {
     double altitudeASL;
     double GeodLatitudeDeg;