Copter: fix sanity checks for takeoff altitude

ArduCopter/mode_auto.cpp

@@ -207,12 +207,9 @@ void ModeAuto::takeoff_start(const Location& dest_loc)
     }
 
     // sanity check target
-    if (alt_target < copter.current_loc.alt) {
-        dest.set_alt_cm(copter.current_loc.alt, Location::AltFrame::ABOVE_HOME);
-    }
-    // Note: if taking off from below home this could cause a climb to an unexpectedly high altitude
-    if (alt_target < 100) {
-        dest.set_alt_cm(100, Location::AltFrame::ABOVE_HOME);
+    float alt_target_min_cm = copter.current_loc.alt + (copter.ap.land_complete ? 100 : 0);
+    if (alt_target < alt_target_min_cm ) {
+        dest.set_alt_cm(alt_target_min_cm , Location::AltFrame::ABOVE_HOME);
     }
 
     // set waypoint controller target