Variable stopwrite threshold using kurtosis

A method, comprising:

• measuring a current position error signal;
• calculating a standard deviation or a variance using the current position error signal sample;
• calculating a kurtosis value, using the current position error signal sample or derivative thereof;
• adjusting a threshold value using the kurtosis value;
• comparing the standard deviation or variance to the threshold value;
• enabling writing when the standard deviation or variance does not exceed the threshold value;
• determining a stopwrite threshold based on a standard deviation or a variance at a current position error signal sample when the standard deviation or variance exceeds the threshold value;
• determining whether the current position error signal sample exceeds the stopwrite threshold;
• disabling writing when the current position error signal sample exceeds the stopwrite threshold;
• and
• enabling writing when the current position error signal sample does not exceed the stopwrite threshold.