[XP] Get the ground elevation under the own aircraft

src/xswiftbus/service.cpp

@@ -766,6 +766,13 @@ namespace XSwiftBus
                     sendDBusReply(sender, serial, getAllWheelsOnGround());
                 });
             }
+            else if (message.getMethodName() == "getGroundElevation")
+            {
+                queueDBusCall([ = ]()
+                {
+                    sendDBusReply(sender, serial, getGroundElevation());
+                });
+            }
             else if (message.getMethodName() == "getCom1ActiveKhz")
             {
                 queueDBusCall([ = ]()

src/xswiftbus/service.h

@@ -19,6 +19,7 @@
 #include "datarefs.h"
 #include "messages.h"
 #include "navdatareference.h"
+#include "terrainprobe.h"
 #include <XPLM/XPLMNavigation.h>
 #include <string>
 #include <chrono>
@@ -174,6 +175,9 @@ namespace XSwiftBus
         //! Get whether all wheels are on the ground
         bool getAllWheelsOnGround() const { return m_onGroundAll.get(); }
 
+        //! Get elevation of ground under the plane in meters
+        double getGroundElevation() const { return m_terrainProbe.getElevation(m_latitude.get(), m_longitude.get(), m_elevation.get())[0]; }
+
         //! COM Selection 6/7
         //! @{
         int getComSelection() const { return m_comAudioSelection.get(); }
@@ -333,6 +337,7 @@ namespace XSwiftBus
         int  m_disapperMessageWindowTimeMs = 5000;
         std::chrono::system_clock::time_point m_disappearMessageWindowTime;
         std::vector<CNavDataReference> m_airports;
+        CTerrainProbe m_terrainProbe;
 
         void readAirportsDatabase();
         std::vector<CNavDataReference> findClosestAirports(int number, double latitude, double longitude);

src/xswiftbus/terrainprobe.cpp

@@ -18,6 +18,13 @@ namespace XSwiftBus
 
     CTerrainProbe::~CTerrainProbe() { XPLMDestroyProbe(m_ref); }
 
+    std::array<double, 3> CTerrainProbe::getElevation(double degreesLatitude, double degreesLongitude, double metersAltitude) const
+    {
+        static const std::string callsign = "myself";
+        bool unused = false;
+        return getElevation(degreesLatitude, degreesLongitude, metersAltitude, callsign, unused);
+    }
+
     std::array<double, 3> CTerrainProbe::getElevation(double degreesLatitude, double degreesLongitude, double metersAltitude, const std::string &callsign, bool &o_isWater) const
     {
         double x, y, z;

src/xswiftbus/terrainprobe.h

@@ -36,7 +36,10 @@ namespace XSwiftBus
         //! Get the elevation in meters at the given point in OpenGL space.
         //! \note Due to the Earth's curvature, the OpenGL vertical axis may not be exactly perpendicular to the surface of the geoid.
         //! \return NaN if no ground was detected.
+        //! @{
+        std::array<double, 3> getElevation(double degreesLatitude, double degreesLongitude, double metersAltitude) const;
         std::array<double, 3> getElevation(double degreesLatitude, double degreesLongitude, double metersAltitude, const std::string &callsign, bool &o_isWater) const;
+        //! @}
 
     private:
         XPLMProbeRef m_ref = nullptr;