How should ARPA data be validated against chart or GPS data?

• A. Act immediately based on ARPA data.
• B. Rely on GPS data alone for decisions.
• C. Validate ARPA data after acting.
• D. Compare CPA/TCPA and positions with chart fixes or GPS; resolve discrepancies before acting.

Answer: (D)

Cross-check ARPA data with independent position references before making any maneuver. ARPA provides predicted positions and times to the closest point of approach, but it can be affected by radar errors, target speed estimates, clutter, or misidentification. By comparing the ARPA-derived CPA/TCPA and target positions with chart fixes or GPS-reported positions, you confirm whether the target is truly on a collision course. If there’s a discrepancy, re-check the data, verify radar settings and updates, and resolve the mismatch before acting. This approach keeps decisions anchored to verifiable information rather than relying solely on ARPA, which helps prevent acting on erroneous predictions.