This paper presents a novel method to optimize the angular accuracy of the rotating tables (motion simulators) employed for the calibration of Inertial measurement units (IMU) and Inertial navigation Systems (INS). An example of an accelerometer calibration using such a table is given; it shows the role played by the table accuracy in the reliability of the calibration procedure. The motion simulator precision is mainly dependent on its angular encoder errors, which must be estimated in order to be compensated for. That leads to propose a novel method for the estimation of these encoder errors: this method provides a continuous estimation of the error over 360°, contrary to the existent procedure carried out by means of an interferometer along with a reflecting polygon fixed on the table axis. Some experimental results show the interest of the approach.