An indoor positioning system and method that correlates map locations to respective wireless access point (AP) fingerprints, and wherein each wireless AP fingerprint is a plurality of wireless AP signal measurements associated with the correlated map location. The method includes receiving position-inference data associated with a user; determining a probable location inside the building based on the position-inference data; receiving wireless AP signal measurements detected by a wireless device associated with the user; associating the probable location with the wireless device based on the association between the position-inference data and the user of the wireless device; and updating the wireless AP fingerprint correlated to the probable location using the received wireless AP signal measurements. The method and system use crowd-sourcing to build and refine the wireless AP fingerprints.