Abstract: A method is provided for removing gimbal periodic reorientation (indexing) readout errors in a navigation system having multiple IMUs mounted to a platform. Each IMU has multiple gyroscopes providing attitude outputs. Attitude readout errors bias due to periodic gimbal motions is determined in each IMU along each gyroscope attitude axis. Attitude outputs of the gyroscopes are time-aligned, as necessary. Onset times of indexing of each gyroscope is determined. A difference is formed between gyroscope attitude outputs. Steps in this difference of attitude outputs are assigned to the respective gyroscope causing the step in attitude. Cumulative sums of the steps associated with the respective gyroscopes are formed. The mean and linear trend in the respective cumulative sums are removed from the respective cumulative sums to form the final error correction, corresponding to the time interval associated with the steps.