The invention discloses a positioning device configured to acquire its own GNSS position, the GNSS positions of rovers in an area around the positioning device and the relative positions of the positioning device to the rovers. The positioning device is configured to calculate a best-fit position based on this data and their confidence indexes. The positioning devices may communicate directly or through a navigation assistance centre. The best-fit position may be provided with indexes of confidence, availability and integrity. In some embodiments, the positioning device of the invention may be robust enough to generate commands to the driving controls of an autonomous vehicle.