[nps] get airspeed, pressure and temp from FDM

sw/simulator/nps/nps_fdm.h

@@ -106,6 +106,12 @@ struct NpsFdm {
 
   struct DoubleVect3 wind; ///< velocity in m/s in NED
 
+  double airspeed;         ///< equivalent airspeed in m/s
+  double pressure;         ///< current (static) atmospheric pressure in Pascal
+  double total_pressure;   ///< total atmospheric pressure in Pascal
+  double dynamic_pressure; ///< dynamic pressure in Pascal
+  double temperature;      ///< current temperature in degrees Celcius
+
   // Control surface positions (normalized values)
   float elevator;
   float flap;

sw/simulator/nps/nps_fdm_crrcsim.c

@@ -120,6 +120,10 @@ void nps_fdm_init(double dt)
   fdm.init_dt = dt;
   fdm.curr_dt = dt;
   fdm.nan_count = 0;
+  fdm.pressure = -1;
+  fdm.total_pressure = -1;
+  fdm.dynamic_pressure = -1;
+  fdm.temperature = -1;
 
   init_ltp();
 
@@ -385,6 +389,13 @@ static void decode_gpspacket(struct NpsFdm *fdm, byte *buffer)
   fdm->ltp_ecef_vel = vel;
   ecef_of_ned_vect_d(&fdm->ecef_ecef_vel, &ltpdef, &vel);
 
+  /* No airspeed from CRRCSIM?
+   * use ground speed for now, since we also don't know wind
+   */
+  struct DoubleVect3 ltp_airspeed;
+  VECT3_COPY(ltp_airspeed, vel);
+  fdm.airspeed = double_vect3_norm(&ltp_airspeed);
+
   /* gps position (1e7 deg to rad and 1e3 m to m) */
   struct LlaCoor_d pos;
   pos.lon = (double)LongOfBuf(buffer, 15) * 1.74533e-9;

sw/simulator/nps/nps_fdm_jsbsim.cpp

@@ -40,6 +40,8 @@
 #include <models/FGPropulsion.h>
 #include <models/FGGroundReactions.h>
 #include <models/FGAccelerations.h>
+#include <models/FGAuxiliary.h>
+#include <models/FGAtmosphere.h>
 #include <models/FGFCS.h>
 #include <models/atmosphere/FGWinds.h>
 
@@ -67,6 +69,9 @@
 #define MetersOfFeet(_f) ((_f)/3.2808399)
 #define FeetOfMeters(_m) ((_m)*3.2808399)
 
+#define PascalOfPsf(_p) ((_p) * 47.8802588889)
+#define CelsiusOfRankine(_r) (((_r) - 491.67) / 1.8)
+
 /** Name of the JSBSim model.
  *  Defaults to the AIRFRAME_NAME
  */
@@ -436,6 +441,15 @@ static void fetch_state(void)
   const FGColumnVector3 &fg_wind_ned = FDMExec->GetWinds()->GetTotalWindNED();
   jsbsimvec_to_vec(&fdm.wind, &fg_wind_ned);
 
+  /*
+   * Equivalent Airspeed, atmospheric pressure and temperature.
+   */
+  fdm.airspeed = MetersOfFeet(FDMExec->GetAuxiliary()->GetVequivalentFPS());
+  fdm.pressure = PascalOfPsf(FDMExec->GetAtmosphere()->GetPressure());
+  fdm.total_pressure = PascalOfPsf(FDMExec->GetAuxiliary()->GetTotalPressure());
+  fdm.dynamic_pressure = PascalOfPsf(FDMExec->GetAuxiliary()->Getqbar());
+  fdm.temperature = CelsiusOfRankine(FDMExec->GetAtmosphere()->GetTemperature());
+
   /*
    * Control surface positions
    *

sw/simulator/nps/nps_sensor_airspeed.c

@@ -67,14 +67,8 @@ void nps_sensor_airspeed_run_step(struct NpsSensorAirspeed *airspeed, double tim
     return;
   }
 
-  /* super simple approximation for now:
-   * airspeed = ground speed + wind
-   */
-  struct DoubleVect3 ltp_air_vel;
-  VECT3_SUM(ltp_air_vel, fdm.ltpprz_ecef_vel, fdm.wind);
-  double speed = double_vect3_norm(&ltp_air_vel);
-  /* sensor offset */
-  airspeed->value = speed + airspeed->offset;
+  /* equivalent airspeed + sensor offset */
+  airspeed->value = fdm.airspeed + airspeed->offset;
   /* add noise with std dev meters/second */
   airspeed->value += get_gaussian_noise() * airspeed->noise_std_dev;
   /* can't be negative, min is zero */