A mobile device collects data, which enables a generation of a radio map for a site. The collection comprises detecting at least one indication of a floor, at which a user is located, in a user input; and performing measurements on radio signals to obtain for each of a plurality of locations of the site a set of characteristics of radio signals. The mobile device receives, during the collection of data, data from a barometer, verifies a most recent indication of a floor in a user input based on changes in the data from the barometer, and outputs a warning to the user in the case of a discrepancy. The mobile device associates each set of characteristics with a floor indicated by a user. The mobile device provides the sets of characteristics and their association with a floor for a generation a radio map supporting a positioning at the site.
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