A telecommunications system comprises a terrestrial repeater (TR) telecommunication network, a satellite positioning network (CS) which delivers signals containing navigation data, and mobile communication terminals (UE) comprising reception and calculation means (DPS) which can determine the respective positions thereof from said signals, and the navigation data that they contain, in addition to communication means (RH) which can receive communication data frames from the telecommunication network. The communication network integrates additional navigation data in chose locations of some of the data frames in order to create increased data frames. The mobile terminals (UE) also comprises extraction means (ME) which are used to extract additional navigation data contained in the increased data frames received by the communication means (RH) and to send them to the reception and calculation means (DPS) so that they can determine the positions of the associated terminals (UE) from the navigation data and additional navigation data.