A satellite navigation receiver does not measure distance directly. It listens for a timing signal from each satellite it can see and works out how long the signal took to arrive. Because the signal travels at the speed of light, an error of a single millionth of a second puts the answer out by three hundred metres. The satellites therefore carry atomic clocks accurate to a few billionths of a second a day, and the ground stations correct them constantly. What looks to the user like a simple question of position is answered, underneath, as a question about time.
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Correct answer to question 26 (Paragraph Comprehension): The system's accuracy depends on keeping clocks precise
Method
The passage builds toward its closing line, that position is really a question about time, and the atomic clocks exist for exactly that reason. It places the clocks on the satellites, not in the receiver.
Updated: November 2026
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