of an upper and lower bound if the input values do not satisfy the values of the upper and lower bound the imu sensor data subdetector 440 issues a fault at 850 the upper and lower bounds may be variable and are predetermined in the system if the input values satisfy the values of the upper and lower bound the operation ends at 840 turning now to fig9 flowchart 900 illustrates the method of operation of the estimator update quality subdetector in the fault detector of fig4 in accordance with an illustrative embodiment of the disclosure the estimator update quality subdetector 450 of fig4 reviews filter statistics output from the filter to determine whether the filter is running properly and able to provide stable 6dof pose estimates the method of estimator update quality subdetector 450 begins operation at 910 with the input of sensor data and filter statistics at 920 at 925 the estimator update quality subdetector 450 checks whether a filter update has failed if a filter update has failed at 930 the estimator update quality subdetector 450 sends a fault if the filter update has not failed at 935 the estimator update quality subdetector 450 checks whether the gyroscope has a fast rotation if the gyroscope has a fast rotation then the estimator update quality.