AC_PrecLand: remove check of type when using distance-to-target

libraries/AC_PrecLand/AC_PrecLand.cpp

@@ -162,10 +162,11 @@ void AC_PrecLand::update(float rangefinder_alt_cm, bool rangefinder_alt_valid)
             Vector3f target_vec_unit_ned = _attitude_history.front() * Rz * target_vec_unit_body;
 
             bool target_vec_valid = target_vec_unit_ned.z > 0.0f;
+            bool alt_valid = (rangefinder_alt_valid && rangefinder_alt_cm > 0.0f) || (_backend->distance_to_target() > 0.0f);
 
-            if (target_vec_valid && ( (rangefinder_alt_valid && rangefinder_alt_cm > 0.0f) || ((enum PrecLandType)(_type.get()) == PRECLAND_TYPE_COMPANION && _backend->distance_to_target()) ) ) {
+            if (target_vec_valid && alt_valid) {
                 float alt;
-                if ((enum PrecLandType)(_type.get()) == PRECLAND_TYPE_COMPANION && _backend->distance_to_target()) {
+                if (_backend->distance_to_target() > 0.0f) {
                     alt = _backend->distance_to_target();
                 } else {
                     alt = MAX(rangefinder_alt_cm*0.01f, 0.0f);

libraries/AC_PrecLand/AC_PrecLand_Backend.h

@@ -33,8 +33,8 @@ public:
     // return true if there is a valid los measurement available
     virtual bool have_los_meas() = 0;
 
-    // return distance to target
+    // returns distance to target in meters (0 means distance is not known)
-    virtual float distance_to_target() = 0;
+    virtual float distance_to_target() { return 0.0f; };
 
     // parses a mavlink message from the companion computer
     virtual void handle_msg(mavlink_message_t* msg) {};

libraries/AC_PrecLand/AC_PrecLand_Companion.h

@@ -31,8 +31,8 @@ public:
     // return true if there is a valid los measurement available
     bool have_los_meas();
     
-    // return distance to target
+    // returns distance to target in meters (0 means distance is not known)
-    float distance_to_target();
+    float distance_to_target() override;
 
     // parses a mavlink message from the companion computer
     void handle_msg(mavlink_message_t* msg);