A global navigation satellite system (“GNSS”) positioning method is provided, based upon a GNSS radio signal that comprises a navigation message transmitted as a succession of data packets. Each data packet is present in the GNSS radio signal as a sequence of symbols obtained by application of a code preceded by a synchronization symbol header. The data packets are organized internally into data fields. At least certain data packets of the succession of data packets contain a synchronization bit field translated by application of the code into a synchronization symbol pattern.