In one embodiment, obstacles in {TAIL ~ the route area} are identified and {HEAD ~ corresponding forbidden areas} are demarcated 
In one embodiment , obstacles in { TAIL ~ the route area } are identified and { HEAD ~ corresponding forbidden areas } are demarcated
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH