A positioning server has a positioning database. The positioning database is configured to store information relating wireless local area network (WLAN) access point (AP) signal measurements to points of a geographic positioning grid. motion information provided by dead-reckoning systems of a plurality of wireless devices and reference location information provided by at least one of a satellite positioning system and a wireless local area network (WLAN) positioning system of each wireless device is also stored. WLAN access point (AP) signal measurements acquired by each wireless device in correspondence with the motion information is stored as are non-causally determine positions of the wireless devices based on the motion information and reference locations. Positioning server is also configured to generate a geographic positioning grid that relates the AP signal measurements to points of the positioning grid based on the determined positions.