A respective preferred installation height above ground level is determined for each of a plurality of locations for a subscriber module for receiving a radio link from an access point in a wireless network, the access point having a given height above ground level and a specified location, and the subscriber module being situated within a given geographical area including the location of the access point. The method comprises accessing elevation data for the given geographical area, processing the elevation data to generate a preferred height data file representing a preferred height for a subscriber module to be wirelessly visible by the access point at each of the plurality of locations and processing the required height data file to provide output data indicating the preferred height of the subscriber module as a function of location.