Which monitoring feature triggers an alarm if the primary and secondary position sources exceed a set distance?

• A. The speed difference between sources exceeds a threshold
• B. The distance between primary and secondary position sources exceeds a set distance
• C. The bearing difference between sources exceeds a threshold
• D. The AIS mismatch between sources

Answer: (B)

The idea being tested is how two independent position references are checked for agreement. If the reported location from the primary source and the secondary source are separated by more than a preset distance, that discrepancy triggers an alarm. This directly flags potential sensor faults, drift, or spoofing because under normal conditions the two estimates should be close to each other within the system’s expected accuracy. The distance threshold is set to match how accurate both sources are expected to be; if they stay within that range, there’s no alarm, but crossing it indicates a meaningful inconsistency. The other options don’t focus on comparing two position reports in space: speed difference, bearing difference, and AIS data mismatch are different kinds of checks and don’t represent the specific position-consistency alarm described here.