What is a key weakness of the INS?

• A. It relies on external navigation updates
• B. There is no outside verification of accuracy
• C. It is extremely loud
• D. It uses ground-based beacons

Answer: (B)

Inertial navigation systems derive position by integrating measured accelerations over time, so tiny errors in the sensors or in initial alignment accumulate, causing drift in velocity and position. Because it’s self-contained and hasn’t an absolute reference to confirm its accuracy, there’s no outside check to verify whether the current readings are truly correct unless another navigation aid is used to correct the drift.

That makes the lack of outside verification of accuracy the best description of a key weakness. The other options don’t fit: relying on external navigation updates would actually help, not be a weakness; being loud isn’t relevant to navigation accuracy; and ground-based beacons aren’t a defining part of a standard INS.