Which statement describes the elements of a single difference solution in GPS?

• A. It removes receiver clock bias by differencing between satellites.
• B. It cancels receiver clock bias by differencing measurements from two receivers to the same satellite.
• C. It uses only one receiver with two satellites.
• D. It does not require any satellite clock information.

Answer: (B)

A single-difference observable comes from subtracting the pseudorange measurement of one receiver from that of another receiver for the same satellite. This cancels the satellite’s clock error because that error affects both receivers in the same way, leaving a measurement that depends on the baseline between the receivers and the difference in their receiver clock biases. In practice, with measurements from at least two satellites, you can solve for the baseline (the geometry) and the receiver clock bias differences.

So the key point is that the satellite clock error is removed by the difference, not the receiver clock bias. The remaining unknowns are the baseline and the difference in the receivers’ clocks, which is why you need at least two satellites to obtain a solvable system.