What is clock bias in GNSS receivers?

• A. The difference between receiver clock and true GPS time estimated by the filter
• B. The difference between satellite clock and GPS time
• C. Receiver bandwidth setting
• D. Antenna phase center variation

Answer: (B)

Clock bias is the difference between the receiver’s local time and GPS time. The receiver’s internal oscillator isn’t perfectly synchronized with GPS time, so its clock has a bias that the navigation solution estimates as an unknown along with the receiver’s position. In the pseudorange model, the measured pseudorange includes the true geometric range plus c times the difference between the receiver’s clock bias and the satellite’s clock bias, plus other errors. The receiver bias is expressed in seconds and can be converted to distance by multiplying by the speed of light. Satellite clock bias, on the other hand, is the deviation of the satellite’s own clock from GPS time and is a separate quantity provided to aid corrections.