AC_Avoidance: get Vector3f when checking all components of relpos

libraries/AC_Avoidance/AP_OADatabase.cpp

@@ -151,16 +151,14 @@ void AP_OADatabase::queue_push(const Vector3f &pos, uint32_t timestamp_ms, float
     // check if this obstacle needs to be rejected from DB because of low altitude near home
 #if APM_BUILD_COPTER_OR_HELI
     if (!is_zero(_min_alt)) { 
-        Vector2f current_pos;
-        if (!AP::ahrs().get_relative_position_NE_home(current_pos)) {
+        Vector3f current_pos;
+        if (!AP::ahrs().get_relative_position_NED_home(current_pos)) {
             // we do not know where the vehicle is
             return;
         }
-        if (current_pos.length() < AP_OADATABASE_DISTANCE_FROM_HOME) {
+        if (current_pos.xy().length() < AP_OADATABASE_DISTANCE_FROM_HOME) {
             // vehicle is within a small radius of home 
-            float height_above_home;
-            AP::ahrs().get_relative_position_D_home(height_above_home);
-            if (-height_above_home < _min_alt) {
+            if (-current_pos.z < _min_alt) {
                 // vehicle is below the minimum alt
                 return;
             }