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SESK: Stuff Everyone Should Know · sesk.info/pilot-traffic-advisory-clock

ATC says 'traffic 12 o'clock.' That clock position is based on what?

Your ground track, rather than the direction the nose points.

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  1. Your magnetic heading
  2. Your true course on the chart
  3. Your ground track ✔

Why: Radar shows where you are going over the ground, not where your nose points. If you are crabbing into a crosswind, the traffic may appear a little off from the clock position given.

Huh, didn't know that: Traffic calls give clock position, distance in miles, direction of travel, and the type and altitude if known.

The dad joke
ATC said traffic at 12 o'clock. I said great, just in time for lunch.
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References

Answer: Your ground track. Radar shows where you are going over the ground, not where your nose points. If you are crabbing into a crosswind, the traffic may appear a little off from the clock position given.

  1. AIM Chapter 4 Section 1, Services Available to Pilots www.faa.gov/air_traffic/publications/atpubs/aim_html/chap4_section_1.html
    Since the radar controller can only observe aircraft track (course) on the radar display, traffic advisories are issued accordingly
    Checked 2026-10-09.

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