Why does the PPP output in kinematic mode include a forward and a backward solution?
The backward solution uses the best estimates of the carrier-phase ambiguities obtained from the forward solution. The backward ‘smoothing’ improves the estimates of the parameters in the initial portion of the forward solution and following data breaks, when ambiguities are converging and the solution is not yet optimal. Normally ambiguities converge to their correct values within 30 minutes of the session start time or within a few minutes following a data break. Convergence time may vary depending on satellite geometry, quality of the observations, the duration of a data outage and the validity of the a-priori estimates of the parameters.
