A method of calibrating an inertial unit comprising an inertial core having three gyros (9, 10, 11) mounted relative to one another so as to have sensing axes (X, Y, Z) that are substantially mutually perpendicular, the gyros being vibratory axisymmetric gyros connected to means for setting them into vibration and for adjusting an angular orientation of a vibration axis about the sensing axis, the method being characterized in that it comprises the steps of: • starting from a first position, causing the inertial core to pivot towards a second position about a pivot axis that is not in alignment with the sensing axes and that is not in alignment with a trisector of said sensing axes, the gyros (9, 10, 11) having errors that appear at frequencies that are not identical; - between the first and second positions, taking measurements of the angular orientation of the vibration axis of each gyro (9, 10, 11), with the angular orientation being left free; - returning the inertial core to the first position; - adjusting the angular orientation of the vibration axis of each gyro to a value corresponding to the second position; - causing the inertial core to pivot towards the second position about the pivot axis; - taking measurements of the angular orientation of the vibration axis of each gyro (9, 10, 11) during pivoting of the inertial core, angular orientation being left free during pivoting; and - calibrating the inertial core as a function of the measurements taken. • starting from a first position, causing the inertial core to pivot towards a second position about a pivot axis that is not in alignment with the sensing axes and that is not in alignment with a trisector of said sensing axes, the gyros (9, 10, 11) having errors that appear at frequencies that are not identical; - between the first and second positions, taking measurements of the angular orientation of the vibration axis of each gyro (9, 10, 11), with the angular orientation being left free; - returning the inertial core to the first position; - adjusting the angular orientation of the vibration axis of each gyro to a value corresponding to the second position; - causing the inertial core to pivot towards the second position about the pivot axis; - taking measurements of the angular orientation of the vibration axis of each gyro (9, 10, 11) during pivoting of the inertial core, angular orientation being left free during pivoting; and - calibrating the inertial core as a function of the measurements taken. - between the first and second positions, taking measurements of the angular orientation of the vibration axis of each gyro (9, 10, 11), with the angular orientation being left free; - returning the inertial core to the first position; - adjusting the angular orientation of the vibration axis of each gyro to a value corresponding to the second position; - causing the inertial core to pivot towards the second position about the pivot axis; - taking measurements of the angular orientation of the vibration axis of each gyro (9, 10, 11) during pivoting of the inertial core, angular orientation being left free during pivoting; and - calibrating the inertial core as a function of the measurements taken.