methods and associated apparatus and programs for computers for operating geolocation devices are provided . the methods include determining the duration of a time interval during which the device is configured to remain active , responsive to a comparison between an estimate of benefit of remaining on for that time interval and an estimate of cost of remaining on for that time interval . the estimates of cost and benefit may be determined in response to user - selected parameters where by the end - user may effect a trade - off between battery life and receiver sensitivity . the methods also include varying the maximum duration of each listening period whereby to conserve battery power .