Plane: bug fix for relative alt

ArduPlane/GCS_Mavlink.pde

@@ -1447,7 +1447,7 @@ void GCS_MAVLINK::handleMessage(mavlink_message_t* msg)
         // convert mission command to mavlink mission item packet
         mavlink_mission_item_t ret_packet;
         memset(&ret_packet, 0, sizeof(ret_packet));
-        if (!AP_Mission::mission_cmd_to_mavlink(cmd, ret_packet, false)) {
+        if (!AP_Mission::mission_cmd_to_mavlink(cmd, ret_packet, true)) {
             goto mission_item_send_failed;
         }
 
@@ -1688,7 +1688,7 @@ mission_item_send_failed:
         if (mavlink_check_target(packet.target_system,packet.target_component)) break;
 
         // convert mavlink packet to mission command
-        if (!AP_Mission::mavlink_to_mission_cmd(packet, cmd, false)) {
+        if (!AP_Mission::mavlink_to_mission_cmd(packet, cmd, true)) {
             result = MAV_MISSION_ERROR;
             goto mission_failed;
         }

ArduPlane/commands.pde

@@ -35,9 +35,15 @@ static void set_next_WP(const AP_Mission::Mission_Command& cmd)
         // additionally treat zero altitude as current altitude
         if (next_WP.content.location.alt == 0) {
             next_WP.content.location.alt = current_loc.alt;
+            next_WP.content.location.flags.relative_alt = false;
         }
     }
 
+    // convert relative alt to absolute alt
+    if (next_WP.content.location.flags.relative_alt) {
+        next_WP.content.location.flags.relative_alt = false;
+        next_WP.content.location.alt += home.alt;
+    }
 
     // are we already past the waypoint? This happens when we jump
     // waypoints, and it can cause us to skip a waypoint. If we are