// schedule a needed buckets for loading
-void FGTileMgr::schedule_needed( double vis, SGBucket curr_bucket) {
+void FGTileMgr::schedule_needed( double vis, const SGBucket& curr_bucket) {
// sanity check (unfortunately needed!)
if ( longitude < -180.0 || longitude > 180.0
|| latitude < -90.0 || latitude > 90.0 )