Counting device and corresponding method

A counting device comprising a memory (4) arranged to receive a set of data in relation to geographical areas together forming a grid of a geographical space, mobile telephony location cell data associating a location cell identifier, a location cell position and a location cell geographical coverage, an anonymizer (6) arranged to determine, for a given location cell, one or more geographical areas overlapping the geographical coverage of the given location cell, and to compute a detection quantum for each geographical area, and a counter (8) arranged to receive mobile telephony signaling data associating, each time, a mobile telephony identifier, a location cell identifier and a time marker, and to determine, for a given time range, a count of mobile telephony devices for each geographical area based on the mobile telephony signaling data and the one or more detection quantums associated with each geographical area, wherein the anonymizer (6) is arranged to modify the geographical coverage of each given location cell by determining an effective radius based on the density of location cells around the given location cell.