Ranging signals are transmitted from GPS satellites to allow the receiver to determine which measurement?

• A. The satellite's orbital velocity.
• B. Range (distance) from each satellite.
• C. The timestamps for system time.
• D. The signal's polarization.

Answer: (A)

Ranging signals measure the distance to GPS satellites. The satellites transmit a precisely timed code, and the receiver compares the transmit time with the receive time to determine how long the signal took to travel. Multiplying that travel time by the speed of light yields the range (distance) to each satellite. This distance information, used from multiple satellites, is what’s needed to compute your position and also to solve for the receiver’s clock bias. Doppler shifts of the carrier relate to velocity, not the basic ranging distance, and polarization isn’t used to determine range. The measurement provided by ranging signals is therefore the distance to each satellite.