This application discloses a GNSS rover having a data receiver, a position processor and a vector error reverser. The data receiver receives GNSS position-determination reference data based on a reference erroneous position having one or more keyed intentional errors made confidential with confidential error keys. The position processor uses the GNSS position-determination reference data to determine a rover erroneous position corresponding to the reference erroneous position. The vector error reverser uses confidential access to at least one confidential error key to reverse the corresponding confidential keyed intentional error in the rover erroneous position to determine a subscribed rover position.