What does signal-to-noise ratio (SNR) represent in GNSS signals, and what is its effect on positioning?

• A. The total power of the signal.
• B. The difference between signal and noise amplitude.
• C. The ratio of signal power to noise; higher SNR yields more reliable measurements and better positioning.
• D. A measure of system bandwidth.

Answer: (C)

Signal-to-noise ratio in GNSS represents how strong the received navigation signal is relative to the background noise. It's the ratio of signal power to noise power. When this ratio is high, the measurements derived from the signal—such as pseudorange and carrier-phase—are less affected by random noise, so the receiver can estimate position more accurately and with greater reliability. If SNR is low, noise dominates, increasing measurement noise, which degrades positioning accuracy and can slow convergence or cause loss of lock. SNR is not simply the total signal power, nor the raw difference in amplitudes, nor a direct measure of bandwidth; it specifically captures how clean the observations are by comparing signal strength to noise.