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