On the morning of 17th February, 2025, Dr. Guo Jiang from the Royal Observatory of Belgium was invited by Researcher Geng Jianghui to give a lecture on ‘Feasibility Study of Integer Precision Single-Point Positioning for UTC Time Maintenance’ at the Innovation Academy for Precision Measurement Science and Technology, CAS (APM). Academician Sun Heping, Professor Zhong Min, Researcher Zhang Zizhan, Associate Researcher Li Guangcai, Postdoctoral Fellow Wen Qiang and other experts and scholars attended the meeting.

    Guo Jiang is an assistant researcher at the Royal Observatory of Belgium, where he is involved in the maintenance of atomic time and Universal Time Coordinated (UTC) under the responsibility of the Bureau International des Poids et Mesures (BIPM), as well as the maintenance of the real-time phase deviation data stream of Wuhan University in the IGS-RT.

    This academic report covers the concept of time-frequency transfer and commonly used time-frequency comparison methods, and discusses the problems and solutions encountered by Integer Precision Single Point Positioning (IPPP) in high-precision time-frequency transfer. It is pointed out that commonly used time-frequency comparison methods, such as two-way time-frequency transmission (TWTFT), PPP-RTK and optical fiber time-frequency transmission, are all limited by co-viewing satellites, the number of deployed stations and physical links, and are unable to carry out long-distance clock comparisons. In this context, the integer precision single-point positioning is not limited by the distance, and can use the millimeter carrier phase observation to achieve high-precision frequency transfer, which also encounters the problem of time-frequency transfer accuracy limitation caused by the discontinuity of the day boundary of the precision products, etc. Finally, the report explored the scheme to improve the time-frequency transfer accuracy of IPPP.

    After the presentation, the participants, including Academician Sun Heping, Professor Zhong Min, Researcher Zhang Zizhan, Associate Researcher Li Guangcai and Postdoctoral Fellow Wen Qiang, exchanged and discussed many details of the content with Dr Guo Jiang, which were beneficial to all of them.