A method of estimating a location of a WLAN-enabled user-device in a WLAN-based positioning system is provided. The WLAN-enabled device receives signals transmitted by WLAN-enabled access points in range of the WLAN-enabled user-device so that observed WLAN-enabled access points identify themselves. The method includes accessing a master database that associates WLAN-enabled access points with corresponding audited locations as determined by an audit of a relatively large geographic area and obtaining location information for any identified WLAN-enabled access point. The method includes accessing a supplemental database to obtain inferred location information corresponding to any identified WLAN-enabled access point. The supplemental database has a relatively small set of WLAN-enabled access points and corresponding inferred locations. The inferred locations are inferred based on input by a user of the WLAN-based positioning system. The method includes estimating a location of the WLAN-enabled user-device based on the audited location information and the inferred location information.