Methods and apparatus are presented for determining a position of an antenna of a GNSS rover from observations of GNSS signals collected at the antenna over multiple epochs and from correction data for at least one of the epochs. A first-epoch rover position relative to a moving base location is determined, a second-epoch update of the first-epoch rover position relative to the moving base location for a second epoch is determined using a single-differenced delta phase process, and the first-epoch position and the second-epoch update are combined to obtain a second-epoch rover position relative to a moving base location of the second epoch.