ESDU TM 185 presents a method for the determination of air data calibrations from an aircraft equipped with an EGI@ which is an embedded Global Positioning System and Inertial Navigation System. The air data sensors that the method is applied to are the angle of attack@ sideslip and Pitot-static probes. Parameters that are derived include true airspeed@ angle of attack@ angle of sideslip and the static pressure error. The document provides background information for some of the techniques defined in ESDU 17013@ ??Aircraft performance from flight test. Part 3: in-flight calibration of an angle of attack sensor??.