by Nadya Goldovsky
Measurement uncertainty for a GPS receiver depends on the receiver’s design and on the measurement method used. The majority of clients’ GPS receivers operate with C/A code and use the one-way method having relatively low metrological parameters. The frequency stability for a GPS receiver expressed by Allan Deviation is larger than that for Cs-standard by 2-3 orders within a short-term interval (1-1000 s), and by one order within a long-term interval of about one day. A GPS receiver’s time scale bias from the Coordinated Universal Time (UTC) can be in order of microseconds. Two user’s GPS receivers can yield different frequency and time results even when connected to the same antenna at the same location because of the difference in performance. Not every GPS receiver is suitable for use as a traceable frequency and/or time standard. Moreover, traceability to the National Time and Frequency Standard is required. Therefore, GPS receiver calibration against the National Time and Frequency Standard (for example, the Cs-atomic clock) traceable to UTC via high accuracy GPS technique is of great importance and implies the calibration of both frequency and time scale.
