US Patent 10031233 GNSS reference for subscribed precisions

This application discloses a GNSS reference apparatus having a vector error generator and a reference data server. The vector error generator generates one or more sequences of keyed intentional errors made confidential with confidential error keys, and then combines the sequences to generate a sequence of reference erroneous positions. The reference data server issues GNSS position-determination reference data based on the reference erroneous positions where the keyed intentional errors for at least one of the confidential sequences are reversible with confidential access to the corresponding confidential error key for determining a GNSS-based position.