Apparatus for determining positional information relating to an object, comprising: means for receiving, comprising a plurality of receiving elements; detection means for detecting signals received at the receiving elements and for generating output signals representative of the received signals; and processing means operable to apply, for each receiving element, a process to the output signal generated from the signal received at that receiving element separately from any output signal generated from a signal received at any other receiving element, so as to obtain a respective value of a parameter representative of the signal received at that receiving element, the processing means being further operable to compare the values of the parameter thus obtained so as to, obtain positional information relating to the object.