An apparatus and method are disclosed in connection with a mobile device locating a wireless local area network (WLAN) associated with a wireless wide area network (WWAN). These concepts involve obtaining and recording maximum and minimum geometric time differences (GTDs) for a pair or pairs of transmitters in the WWAN while coverage is provided by the WLAN, and using these differences to later compare a contemporaneous GTD to determine whether the mobile device is more likely within the coverage area of the WLAN.