A method comprising, performed by at least one apparatus: obtaining (201, 511) fingerprints that have been collected by at least one mobile device for supporting a positioning of other mobile devices, each fingerprint comprising results of measurements on radio signals of at least one communication node at a particular location and an indication of the particular location; selecting some of the obtained fingerprints as test fingerprints; generating, based on the obtained fingerprints excluding the test fingerprints, a radio model supporting a positioning of mobile devices that are configured to perform measurements on radio signals of communication nodes; estimating for results of measurements in each of the test fingerprints a location of measurements based on the generated radio model; comparing for each test fingerprint the estimated location with the particular location indicated in the test fingerprint, wherein comparing for a respective test fingerprint the estimated location with the indication of the particular location in the test fingerprint comprises at least one of: (i) determining at least one discrepancy between the estimated location and the particular location, (ii) determining a distance between a horizontal component of the estimated location and a horizontal component of the particular location; (iii) determining a difference in height between an altitude component of the estimated location and an altitude component of the particular location; and (iv) determining a difference in floor number of a floor corresponding to an altitude component of the estimated location and a floor corresponding to an altitude component of the particular location; determining (202, 516) a positioning quality that can be achieved in a positioning which is based on obtained fingerprints collected by the at least one mobile device, wherein a result of the comparison forms a basis of the positioning quality; and generating (203, 522), based on the determined positioning quality, a feedback to a user of the at least one mobile device, the feedback indicating whether further fingerprints should be collected. obtaining (201, 511) fingerprints that have been collected by at least one mobile device for supporting a positioning of other mobile devices, each fingerprint comprising results of measurements on radio signals of at least one communication node at a particular location and an indication of the particular location; selecting some of the obtained fingerprints as test fingerprints; generating, based on the obtained fingerprints excluding the test fingerprints, a radio model supporting a positioning of mobile devices that are configured to perform measurements on radio signals of communication nodes; estimating for results of measurements in each of the test fingerprints a location of measurements based on the generated radio model; comparing for each test fingerprint the estimated location with the particular location indicated in the test fingerprint, wherein comparing for a respective test fingerprint the estimated location with the indication of the particular location in the test fingerprint comprises at least one of: (i) determining at least one discrepancy between the estimated location and the particular location, (ii) determining a distance between a horizontal component of the estimated location and a horizontal component of the particular location; (iii) determining a difference in height between an altitude component of the estimated location and an altitude component of the particular location; and (iv) determining a difference in floor number of a floor corresponding to an altitude component of the estimated location and a floor corresponding to an altitude component of the particular location; (i) determining at least one discrepancy between the estimated location and the particular location, (ii) determining a distance between a horizontal component of the estimated location and a horizontal component of the particular location; (iii) determining a difference in height between an altitude component of the estimated location and an altitude component of the particular location; and (iv) determining a difference in floor number of a floor corresponding to an altitude component of the estimated location and a floor corresponding to an altitude component of the particular location; determining (202, 516) a positioning quality that can be achieved in a positioning which is based on obtained fingerprints collected by the at least one mobile device, wherein a result of the comparison forms a basis of the positioning quality; and generating (203, 522), based on the determined positioning quality, a feedback to a user of the at least one mobile device, the feedback indicating whether further fingerprints should be collected.