A positioning method carried out by a positioning apparatus, the positing method comprising a. obtaining an approximate rover anchor position (U' (1.0)) for a first epoch from an autonomous position solution or a differential position solution of the rover, b. using the approximate rover anchor position (U' (1.0)) to determine a rover position difference (δÛ(1.0,2.0)) from delta phase measurements at the rover between the first epoch and a succeeding epoch, b1. wherein the approximate rover anchor position contains an initial error, wherein the rover position difference (δÛ(1.0,2.0)) for said succeeding epoch contains a respective partial error based on the initial error, c. obtaining an improved rover anchor position for the first epoch, the improved rover anchor position being a synchronous rover anchor position ( (1.0)) becoming available for the first epoch, the synchronous anchor position being accurate to centimeter-level and the approximate rover anchor position being generally accurate to meter-level, thereafter d. deriving an adjusted rover position difference (δ (1.0,2.0)) using said determined rover position difference (δÛ(1.0,2.0)) for said succeeding epoch, d1. wherein deriving the adjusted rover position difference (δ (1.0,2.0)) for said succeeding epoch comprises adding a correction term (γ(1.0,2.0)) related to the initial error to said determined rover position difference (δÛ(1.0,2.0)), wherein the initial error is the difference between the improved rover anchor position ( (1.0)) and the approximate rover anchor position (U' (1.0)); and e. deriving a rover position ( (2.0)) for said succeeding epoch from the improved rover anchor position ( (1.0)) for the first epoch and the adjusted rover position difference (δ (1.0,2.0) for said succeeding epoch, e1. wherein deriving the rover position (( (2.0)) for said succeeding epoch comprises adding the adjusted rover position difference (δ (1.0,2.0)) for said succeeding epoch to the improved rover anchor position ( (1.0)) for the first epoch. a. obtaining an approximate rover anchor position (U' (1.0)) for a first epoch from an autonomous position solution or a differential position solution of the rover, b. using the approximate rover anchor position (U' (1.0)) to determine a rover position difference (δÛ(1.0,2.0)) from delta phase measurements at the rover between the first epoch and a succeeding epoch, b1. wherein the approximate rover anchor position contains an initial error, wherein the rover position difference (δÛ(1.0,2.0)) for said succeeding epoch contains a respective partial error based on the initial error, c. obtaining an improved rover anchor position for the first epoch, the improved rover anchor position being a synchronous rover anchor position ( (1.0)) becoming available for the first epoch, the synchronous anchor position being accurate to centimeter-level and the approximate rover anchor position being generally accurate to meter-level, thereafter d. deriving an adjusted rover position difference (δ (1.0,2.0)) using said determined rover position difference (δÛ(1.0,2.0)) for said succeeding epoch, d1. wherein deriving the adjusted rover position difference (δ (1.0,2.0)) for said succeeding epoch comprises adding a correction term (γ(1.0,2.0)) related to the initial error to said determined rover position difference (δÛ(1.0,2.0)), wherein the initial error is the difference between the improved rover anchor position ( (1.0)) and the approximate rover anchor position (U' (1.0)); and e. deriving a rover position ( (2.0)) for said succeeding epoch from the improved rover anchor position ( (1.0)) for the first epoch and the adjusted rover position difference (δ (1.0,2.0) for said succeeding epoch, e1. wherein deriving the rover position (( (2.0)) for said succeeding epoch comprises adding the adjusted rover position difference (δ (1.0,2.0)) for said succeeding epoch to the improved rover anchor position ( (1.0)) for the first epoch.