A method is for WLAN localization and corresponding location based service supply. By providing a WLAN data set as an actual WLAN fingerprint of a geographical unit for the usage in a mobile device the user is enabled to localize himself self-sustained. Thereby the mobile device receives WLAN signals from at least three WLAN senders for the localization. Due to self-sustained identifying of the WLAN senders by the mobile device on basis of the received WLAN signals the mobile device may calculate the actual geographical position of the mobile device. The calculation is done on basis of the WLAN data set and on basis of the received WLAN signals from the at least three different WLAN senders. Furthermore a location based service is supplied by the mobile device the a user of the mobile device on basis of the calculated actual position.