An apparatus for performing Global Navigation Satellite System (GNSS) control includes: a GNSS receiver arranged to obtain/calculate at least one position of the apparatus; and an assistance data provider implemented within the apparatus, wherein the assistance data provider is arranged to provide the GNSS receiver with assistance data for use of obtaining/calculating the at least one position, and the assistance data provider selectively selects a specific assistance mode from a plurality of assistance modes for the GNSS receiver according to at least one predefined rule, with the assistance data corresponding to the specific assistance mode. Associated methods and storage media are also provided.