AC_PrecLand: pass in time corrected LANDING_TARGET msg

should make companion based precision landing more accurate

libraries/AC_PrecLand/AC_PrecLand.cpp

@@ -263,11 +263,11 @@ bool AC_PrecLand::get_target_velocity_relative_cms(Vector2f& ret)
 }
 
 // handle_msg - Process a LANDING_TARGET mavlink message
-void AC_PrecLand::handle_msg(const mavlink_message_t &msg)
+void AC_PrecLand::handle_msg(const mavlink_landing_target_t &packet, uint32_t timestamp_ms)
 {
     // run backend update
     if (_backend != nullptr) {
-        _backend->handle_msg(msg);
+        _backend->handle_msg(packet, timestamp_ms);
     }
 }
 

libraries/AC_PrecLand/AC_PrecLand.h

@@ -86,7 +86,7 @@ public:
     bool target_acquired();
 
     // process a LANDING_TARGET mavlink message
-    void handle_msg(const mavlink_message_t &msg);
+    void handle_msg(const mavlink_landing_target_t &packet, uint32_t timestamp_ms);
 
     // parameter var table
     static const struct AP_Param::GroupInfo var_info[];

libraries/AC_PrecLand/AC_PrecLand_Backend.h

@@ -35,7 +35,7 @@ public:
     virtual float distance_to_target() { return 0.0f; };
 
     // parses a mavlink message from the companion computer
-    virtual void handle_msg(const mavlink_message_t &msg) {};
+    virtual void handle_msg(const mavlink_landing_target_t &packet, uint32_t timestamp_ms) {};
 
     // get bus parameter
     int8_t get_bus(void) const { return _frontend._bus.get(); }

libraries/AC_PrecLand/AC_PrecLand_Companion.cpp

@@ -42,18 +42,14 @@ float AC_PrecLand_Companion::distance_to_target()
     return _distance_to_target;
 }
 
-void AC_PrecLand_Companion::handle_msg(const mavlink_message_t &msg)
+void AC_PrecLand_Companion::handle_msg(const mavlink_landing_target_t &packet, uint32_t timestamp_ms)
 {
-    // parse mavlink message
-    __mavlink_landing_target_t packet;
-    mavlink_msg_landing_target_decode(&msg, &packet);
-
     _distance_to_target = packet.distance;
 
     // compute unit vector towards target
     _los_meas_body = Vector3f(-tanf(packet.angle_y), tanf(packet.angle_x), 1.0f);
     _los_meas_body /= _los_meas_body.length();
 
-    _los_meas_time_ms = AP_HAL::millis();
+    _los_meas_time_ms = timestamp_ms;
     _have_los_meas = true;
 }

libraries/AC_PrecLand/AC_PrecLand_Companion.h

@@ -36,7 +36,7 @@ public:
     float distance_to_target() override;
 
     // parses a mavlink message from the companion computer
-    void handle_msg(const mavlink_message_t &msg) override;
+    void handle_msg(const mavlink_landing_target_t &packet, uint32_t timestamp_ms) override;
 
 private:
     float               _distance_to_target;    // distance from the camera to target in meters