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A detailed comparison of two continuous GPS carrier-phase time transfer techniques



Jian Yao, Judah Levine, Skakun Ivan, Zhiheng Jiang


The wide application of GPS carrier-phase (CP) time transfer is limited by the problem of boundary discontinuity (BD). The discontinuity has two categories. One is "day boundary discontinuity," which has been studied extensively and can be solved by a few methods [1-8]. The other category of discontinuity, called "anomaly boundary discontinuity (anomaly-BD)," comes from a GPS data anomaly. The anomaly can be a data gap (i.e., missing data), a GPS measurement error (i.e., bad data), or a cycle slip. Initial study of the anomaly-BD shows that we can fix the discontinuity if the anomaly lasts no more than 20 min, using the polynomial curve-fitting strategy to repair the anomaly [9]. However, sometimes, the data anomaly lasts longer than 20 min. Thus, a better curve-fitting strategy is in need. Besides, a cycle slip, as another type of the data anomaly, can occur and lead to an anomaly-BD. To solve the above two problem, this paper proposes a new strategy, i.e., the clock-aided curve fitting strategy with the function of cycle slip detection. Basically, this new strategy applies the satellite clock correction to the GPS data. After that, we do the polynomial curve fitting as before. Study shows the residual is ~3 mm for all GPS satellites. The new strategy also detects the cycle slips and finds the slip number by searching the minimum curve-fitting residual. Extensive examples show that this new strategy enables us to repair up to 40-min GPS data anomaly, no matter the anomaly is a data gap or a cycle slip or both. Thus, we greatly improve the robustness of the GPS CP time transfer.


Anomaly boundary discontinuity (anomaly-BD), boundary discontinuity, carrier phase, curve fitting, cycle slip, GPS, precise point positioning (PPP), time transfer


Yao, J. , Levine, J. , Ivan, S. and Jiang, Z. (2015), A detailed comparison of two continuous GPS carrier-phase time transfer techniques, Metrologia (Accessed July 16, 2024)


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Created September 8, 2015, Updated February 19, 2017