A method, non-transitory computer readable medium and a system that includes a confidence level module arranged to calculate, in response to detection signals, estimated upper surface points and to associate a non-binary confidence level with each estimated upper surface point; wherein the detection signals are generated by a receiver in response to an irradiation of at least a portion of the upper surface of the content with radiation pulses transmitted by a transmitter; and an estimator that is arranged to calculate an estimate of the upper surface based upon the estimated upper surface points and the non-binary confidence level associated with each estimated upper surface point.