I. Introduction
An Inertial Navigation System (INS) determines the position, velocity and attitude of a moving platform (aerial or terrestrial) through a processing of the accelerations and angular velocity measurements of an Inertial Measurement Unit (IMU), which consists of two orthogonal sensor triads, one with three accelerometers and the other with three gyroscopes. The two triads are nominally parallel and the origin is defined as the origin of the accelerometer triad.