AP_AHRS: expose EKF setTerrainHgtStable accessor

libraries/AP_AHRS/AP_AHRS.h

@@ -566,6 +566,10 @@ public:
     // false when no limiting is required
     virtual bool get_hgt_ctrl_limit(float &limit) const WARN_IF_UNUSED { return false; };
 
+    // Set to true if the terrain underneath is stable enough to be used as a height reference
+    // this is not related to terrain following
+    virtual void set_terrain_hgt_stable(bool stable) {}
+
     // Write position and quaternion data from an external navigation system
     virtual void writeExtNavData(const Vector3f &pos, const Quaternion &quat, float posErr, float angErr, uint32_t timeStamp_ms, uint16_t delay_ms, uint32_t resetTime_ms) { }
 

libraries/AP_AHRS/AP_AHRS_NavEKF.cpp

@@ -1977,6 +1977,18 @@ bool AP_AHRS_NavEKF::get_hgt_ctrl_limit(float& limit) const
     return false;
 }
 
+// Set to true if the terrain underneath is stable enough to be used as a height reference
+// this is not related to terrain following
+void AP_AHRS_NavEKF::set_terrain_hgt_stable(bool stable)
+{
+#if HAL_NAVEKF2_AVAILABLE
+    EKF2.setTerrainHgtStable(stable);
+#endif
+#if HAL_NAVEKF3_AVAILABLE
+    EKF3.setTerrainHgtStable(stable);
+#endif
+}
+
 // get_location - updates the provided location with the latest calculated location
 //  returns true on success (i.e. the EKF knows it's latest position), false on failure
 bool AP_AHRS_NavEKF::get_location(struct Location &loc) const

libraries/AP_AHRS/AP_AHRS_NavEKF.h

@@ -249,6 +249,10 @@ public:
     // it will return invalid when no limiting is required
     bool get_hgt_ctrl_limit(float &limit) const override;
 
+    // Set to true if the terrain underneath is stable enough to be used as a height reference
+    // this is not related to terrain following
+    void set_terrain_hgt_stable(bool stable) override;
+
     // get_location - updates the provided location with the latest
     // calculated location including absolute altitude
     // returns true on success (i.e. the EKF knows it's latest