A method for calibrating an aircraft attitude and reference heading system installed in an aircraft while the aircraft is positioned at a location on the ground along the Earth's surface , said attitude and reference heading system having an associated attitude for said positioned aircraft and comprising one or more magnetometers, said method comprising the steps of: aligning the aircraft to a known magnetic heading; determining the associated attitude of the one or more magnetometers for said positioned aircraft, wherein the associated attitude includes a pitch angle and bank angle ; obtaining an actual reading from said one or more magnetometers at the known magnetic heading for said positioned aircraft wherein the actual reading includes an x-axis magnetometer reading, a y-axis magnetometer reading, and a z-axis magnetometer reading; obtaining from a database a horizontal intensity and a vertical intensity of the Earth's magnetic field at said location of said positioned aircraft ; computing theoretical values for said one or more magnetometers at said known magnetic heading of said positioned aircraft based on at least said magnetic heading, said associated attitude of the one or more magnetometers for said positioned aircraft, and said obtained horizontal intensity and vertical intensity of the Earth's magnetic field at said location of said positioned aircraft ; subtracting from said obtained actual magnetometer reading for said positioned aircraft at said known magnetic heading said computed values for said one or more magnetometers at said known magnetic heading to obtain hard iron calibration values for said attitude and reference heading system at said known magnetic heading for said positioned aircraft ; and utilizing said obtained hard iron calibration values at said magnetic heading of said aircraft to calibrate said attitude and reference heading system for said aircraft. aligning the aircraft to a known magnetic heading; determining the associated attitude of the one or more magnetometers for said positioned aircraft, wherein the associated attitude includes a pitch angle and bank angle ; obtaining an actual reading from said one or more magnetometers at the known magnetic heading for said positioned aircraft wherein the actual reading includes an x-axis magnetometer reading, a y-axis magnetometer reading, and a z-axis magnetometer reading; obtaining from a database a horizontal intensity and a vertical intensity of the Earth's magnetic field at said location of said positioned aircraft ; computing theoretical values for said one or more magnetometers at said known magnetic heading of said positioned aircraft based on at least said magnetic heading, said associated attitude of the one or more magnetometers for said positioned aircraft, and said obtained horizontal intensity and vertical intensity of the Earth's magnetic field at said location of said positioned aircraft ; subtracting from said obtained actual magnetometer reading for said positioned aircraft at said known magnetic heading said computed values for said one or more magnetometers at said known magnetic heading to obtain hard iron calibration values for said attitude and reference heading system at said known magnetic heading for said positioned aircraft ; and utilizing said obtained hard iron calibration values at said magnetic heading of said aircraft to calibrate said attitude and reference heading system for said aircraft. <EOS>