To calibrate and compensate the compass error of magnetic heading in a carrier with constant pitch Angle, the deviation compensation algorithm (DCA) for magnetic deviation compensation is put forward.

The reason for Projective distortion that the amplification ratio is not constant but has nonlinear relation with pitch and tilt angles and field of view of cameras was found out.

Then the speech signal is pitch adjusted according to this pitch contour, where the original signal with time varying pitch period is converted to a signal of constant pitch period.