{HEAD ~ A method} of determining {TAIL ~ the level} of a material surface in a confined space, from a position above said surface, using an ultrasound transducer positioned above said surface, said method including the steps of: 
of determining
{ HEAD ~ A method } of determining { TAIL ~ the level } of a material surface in a confined space , from a position above said surface , using an ultrasound transducer positioned above said surface , said method including the steps of :
HEAD HEAD HEAD HEAD HEAD HEAD REL REL 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 OTH OTH OTH OTH OTH OTH OTH OTH