MODELING OF CERTAIN STRAPDOWN HEADING-SENSITIVE ERRORS IN INS ERROR MODELS

Self-alignment of a gimbaled inertial navigation system (INS) results in a platform tilt which cancels the effect of the level accelerometer biases. The same cancellation takes place in strapdown INS too; however, unlike gimbaled INS, in a strapdown system, this cancellation is perturbed once the INS changes heading. This note shows that the standard strapdown INS error model does describe this heading-sensitive phenomenon and that the transformation matrix from the body to the reference coordinate system plays a major role in the modeling of this phenomenon.