Method and apparatus for calibration

The present invention provides a method and apparatus for calibrating the rotational relationship between a first motion sensor and a second motion sensor in a sensor system, the method comprises the steps of: determining a minimal number of measurements based on the number of dimensions of the coordinate system of said first motion sensor and the number of dimensions of the coordinate system of said second motion sensor; measuring said sensor system for a specific number of measurements to obtain the output values of said first motion sensor and said second motion sensor during each of the measurements, said specific number of measurements is not less than said minimal number of measurements; and obtaining the rotational relationship between the first motion sensor and the second motion sensor based on said measured output values.