This is in contrast with a system, such as that of Riva referred to above, which measures velocity in vessels lying parallel to the surface and in which only the cells across {TAIL ~ the width} of {HEAD ~ the vessel} are able to contribute to the system 
This is in contrast with a system , such as that of Riva referred to above , which measures velocity in vessels lying parallel to the surface and in which only the cells across { TAIL ~ the width } of { HEAD ~ the vessel } are able to contribute to the system
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 OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH