Why is time synchronization between sensors crucial in a navigation system?

• A. Accurate time tags are optional and do not affect fusion.
• B. Time synchronization issues are negligible in navigation systems.
• C. Misaligned timestamps cause data from different instants to be fused incorrectly, leading to position, velocity, and attitude errors.
• D. Clock synchronization is provided automatically by power cycling.

Answer: (C)

In a navigation system, combining measurements from multiple sensors only makes sense if those measurements refer to the same moment in time. When timestamps are not aligned, data from different instants are fused as if they were simultaneous, and the state estimate (position, velocity, and attitude) is built from information that doesn’t actually correspond to one exact time. Since the system’s state evolves with time, even tiny timing offsets can introduce errors that propagate through the dynamic model and filter, leading to biased or drifting position, velocity, and orientation estimates. High-rate sensors like inertial measurement units are especially sensitive, because their readings drive rapid state updates and any small misalignment compounds quickly. Ensuring accurate time tags and a common time reference prevents these mis-synchronization errors, keeping the fused result consistent. The other ideas—that time tags are optional, that synchronization issues are negligible, or that cycling powers automatically synchronize clocks—don’t hold, because proper synchronization requires deliberate coordination and precise timestamps, not automatic side effects of power cycles.