In the case of a center pivot irrigator, it is preferable that the irrigator travels around {HEAD ~ a stationary temporary reference member}, the reference member being temporarily located in a hole in {TAIL ~ the ground} and including ground engageable anti rotation means which enable the reference member to be fixed relative to motion of the carriages for reference purposes 
In the case of a center pivot irrigator , it is preferable that the irrigator travels around { HEAD ~ a stationary temporary reference member } , the reference member being temporarily located in a hole in { TAIL ~ the ground } and including ground engageable anti rotation means which enable the reference member to be fixed relative to motion of the carriages for reference purposes
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH