The apparatus includes a first or reference station that provides a reference for the survey and whose location is determined with high accuracy, and a second or mobile station that is spaced apart from the first station and acts as {TAIL ~ a mobile measurement unit} for {HEAD ~ the survey} 
The apparatus includes a first or reference station that provides a reference for the survey and whose location is determined with high accuracy , and a second or mobile station that is spaced apart from the first station and acts as { TAIL ~ a mobile measurement unit } for { HEAD ~ the survey }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD