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Sub-10–16 accuracy GNSS frequency transfer with IPPP


Precise point positioning (PPP) using dual-frequency GNSS code and phase measurements has been the technique of choice for time and frequency transfer for more than a decade. Several analysis centers providing the satellite orbit and clock products used in PPP now make use of ambiguity resolution methods that preserve the integer nature of the carrier phase ambiguities, thus allowing the development of integer ambiguity PPP techniques (IPPP). By comparison with independent highly stable time transfer techniques not GNSS based, we show that IPPP provides time transfer stability and frequency transfer accuracy with improved long-term performance of order 7 × 10–16/T, where T is the duration in days of continuous phase measurements, thus reaching the sub − 10–16 level after one week of averaging. This method can readily be put into operation between any two locations equipped with such GNSS receivers which have become ubiquitous equipment in scientific institutes. The analysis procedure is described in some detail, summarizing lessons learned from many years of experience and pointing out the necessary checks and the practical points that are needed to ensure that optimal results will be obtained.

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The datasets generated during the current study are available from the author on a reasonable request.


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I am indebted to Julia Leute, who worked at the BIPM on IPPP developments for two years until June 2019 with support from the French LABEX Cluster of Excellence FIRST-TF (ANR-10-LABX-48-01). She rendered operational the procedures described in this paper and produced some of the IPPP results used in this study. I also thank my colleague Frédéric Meynadier who helps maintaining the software. The GINS software and the necessary GRG satellite products are provided by CNES-CLS, and I thank more particularly Sylvain Loyer and Félix Perosanz for their extended support. The continuous contribution of time laboratories providing GNSS and other data for their participation to UTC is gratefully acknowledged.

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Correspondence to Gérard Petit.

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Petit, G. Sub-10–16 accuracy GNSS frequency transfer with IPPP. GPS Solut 25, 22 (2021).

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  • GPS ambiguity resolution
  • Frequency transfer
  • IPPP