A method comprising, performed by a mobile device : obtaining results of measurements by the mobile device on radio signals transmitted by at least one transmitter , the results of measurements comprising characteristics of the radio signals at each of a plurality of locations of measurements at a particular site, and indications of the locations of measurement; providing the results of measurement and the indications of the locations as a basis for a generation of a radio map for use in supporting a positioning of mobile devices at the site ; detecting in addition a user input to the mobile device , the user input defining a localization area at the site that is to be covered by the radio map ; and providing in addition a representation of the defined localization area for use in connection with the radio map ; characterized by the method further comprising generating the radio map based on the measurement results and the indications of the locations and using the representation of the localization area in connection with the radio map by at least one of: determining a degree of coverage of the radio map within the localization area; determining a degree of coverage of the radio map within the localization area and causing a request for additional measurements in the localization area in case the determined degree of coverage falls short of a predetermined value; determining at least one indication of quality of the radio map in the localization area; determining at least one indication of quality of the radio map in the localization area and causing a request for additional measurements in the localization area in case at least one of the at least one indication of quality falls short of a predetermined value; determining at least one indication of quality of the radio map in the localization area and causing storage of the at least one indication of quality as information on a quality of a positioning that is based on the radio map; and determining a position of the mobile device based on the radio map, while limiting possible positions of the mobile device to the localization area.. obtaining results of measurements by the mobile device on radio signals transmitted by at least one transmitter , the results of measurements comprising characteristics of the radio signals at each of a plurality of locations of measurements at a particular site, and indications of the locations of measurement; providing the results of measurement and the indications of the locations as a basis for a generation of a radio map for use in supporting a positioning of mobile devices at the site ; detecting in addition a user input to the mobile device , the user input defining a localization area at the site that is to be covered by the radio map ; and providing in addition a representation of the defined localization area for use in connection with the radio map ; determining a degree of coverage of the radio map within the localization area; determining a degree of coverage of the radio map within the localization area and causing a request for additional measurements in the localization area in case the determined degree of coverage falls short of a predetermined value; determining at least one indication of quality of the radio map in the localization area; determining at least one indication of quality of the radio map in the localization area and causing a request for additional measurements in the localization area in case at least one of the at least one indication of quality falls short of a predetermined value; determining at least one indication of quality of the radio map in the localization area and causing storage of the at least one indication of quality as information on a quality of a positioning that is based on the radio map; and determining a position of the mobile device based on the radio map, while limiting possible positions of the mobile device to the localization area.. <EOS>