A method, apparatus and computer readable storage medium permit an updated radio map to be determined. In an iteration, the method obtains or holds available current radio map data representing a current radio map for a site and track data of a mobile device. The track data includes sensor data and radio signal observation data representing sets of radio signal observation results captured at different observation positions. The method estimates the observation positions on the track based on the current radio map data and the track data including the sensor data and the radio signal observation data and associates each estimated observation position with a respective set of radio signal observation results represented by the radio signal observation data to determine a sequence of radio fingerprints for the track. The method provides or uses the sequence of radio fingerprints for determining an updated radio map for the site.