GPS Phases: Single Epoch Ambiguity and Slip Resolution
An observational equation of the GPS carrier phase contains the pair station — satellite specific and epoch independent bias γ r s = ψ s (t 0)−ψ r (t 0) +N r s , in which N r s is an integer ambiguity and ψ (t 0), ψr(t 0) are transmitter and receiver initial phases. Through sequential processing of phases we update in each epoch, among other unknowns, the γ r s estimates, provided specific minimal configurations of satellites, stations and already processed epochs are satisfied. All second differences of the phases, e.g. with respect to a given reference satellite and reference receiver, ∇Δγ r s =∇ΔN r s , should be then integers on each L1 and L2 band. These conditions can be solved for all N r s ’s (thus implying new γ r s -values) about current estimates of the γ r s ’s as soon as the integer values are found by means of a proper search procedure.
Cycle slips come into view as outliers of observations produced by rapid changes of particular γ r s values. In that case a new observation sequence is created, for which new γ-parameters are estimated, and then consequently constrained for ambiguities.
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