A system and a method for augmentation of satellite positioning systems wherein a monitoring ground station (MGS) is connected to a computer center in charge of determining the level of error of a satellite (NS) broadcasting positioning signals, and transmitting navigation correction data to a mobile user. The transmission is performed using a digital satellite system using at least one digital satellite (DS) capable of broadcasting multiplexed data in down-link transmission to a user station (U). The user station (U) de-multiplexes and retrieves the navigation correction data from said digital satellite down-link transmission by way of a frame adapter (7) connected to a satellite receiver (6). Specific data such as time or GNSS almanacs are replicated under specific format and put into specific parts of a signaling channel to enable time broadcast to standard receivers of a DS system, and to speed-up acquisition of GNSS satellite signal by standard GNSS receivers possibly in use in the U station. A method is also disclosed for broadcasting time with a reasonable accuracy.