# How are airliners AoA-Sensors calibrated?

Airflow around the fuselage is not free, even near the aircraft nose. I assume some correction is applied to the measured angle to get the corresponding freeflow angle.

How is the reponse curve for this correction obtained (for narrow/wide-body airliners)? There must be some other sensor to compare with. This cannot be GPS, since that would give pitch, not AoA.