If a position discrepancy among three or more Position Reference Systems is detected, what test causes the DP system to reject the drifting PRS?

The correct choice highlights the role of comparison testing within the context of Dynamic Positioning (DP) systems when evaluating position reference systems (PRS). When discrepancies among multiple PRS are detected, the comparison test is conducted to assess the validity of the position data being received from each reference system.

In this scenario, when three or more systems are providing position data and a discrepancy is noted, it is essential to identify which of the systems is providing erroneous information. The comparison test analyzes the input from all systems and determines how they relate to one another. If one system significantly deviates from the others, it is flagged as having a drift or possible malfunction.

Utilizing the comparison test helps ensure that the DP system can maintain accurate positioning by relying only on data from the functioning PRS. By rejecting the drifting system, the DP system can reduce risks associated with positional errors, which is critical for safe vessel operation.

Validation, median, and standard deviation tests may also contribute to the assessment of positioning data; however, the mechanism that specifically identifies and discards data based on comparative analysis among multiple sources is the comparison test. This makes it key in maintaining reliable operations in dynamic positioning situations.