Method and system for compensating for soft iron magnetic disturbances in a heading reference system

A method for compensating for soft iron magnetic disturbances in a heading reference system, the method comprising the steps of:

• receiving a first measurement value associated with a magnetometer;
• receiving a second measurement value associated with a gyroscope;
• determining a first rate of change for magnetometer readings over a time period using the first measurement value and one or more magnetometer measurement values received prior to the first measurement value;
• determining a second rate of change for gyroscope readings over the time period using the second measurement value;
• determining a differential rate of change by subtracting the first rate of change from the second rate of change;
• and
• compensating for soft iron effects on the magnetometer based on a gyroscope reading, if the magnitude of the differential rate of change is greater than a maximum expected drift for the gyroscope.

A system for compensating for soft iron magnetic disturbances in a heading reference system, the system comprising:

• a magnetometer;
• a gyroscope;
• and
• a processor configured to:
• receive a first measurement value associated with the magnetometer;
• receive a second measurement value associated with the gyroscope;
• determine a first rate of change for magnetometer readings over a time period using the first measurement value and one or more magnetometer measurement values received prior to the first measurement value;
• determine a second rate of change for gyroscope readings over the time period using the second measurement value;
• determine a differential rate of change by subtracting the first rate of change from the second rate of change;
• calculate an estimate of attitude and heading using a magnetometer reading, if the magnitude of the differential rate of change is less than a maximum expected drift for the gyroscope;
• and
• calculate an estimate of attitude and heading using a gyroscope reading and a prior heading, if the magnitude of the differential rate of change is greater than the maximum expected drift for the gyroscope.

A method for compensating for soft iron magnetic disturbances in a heading reference system, the method comprising the steps of:

• receiving a first measurement value associated with a magnetometer;
• receiving a second measurement value associated with a gyroscope;
• determining a first rate of change for magnetometer readings over a time period using the first measurement value and one or more magnetometer measurement values received prior to the first measurement value;
• determining a second rate of change for gyroscope readings over the time period using the second measurement value;
• determining a differential rate of change by subtracting the first rate of change from the second rate of change;
• calculating an estimate of attitude and heading using a magnetometer reading, if the magnitude of the differential rate of change is less than a maximum expected drift for the gyroscope;
• and
• calculating an estimate of attitude and heading using a gyroscope reading and a prior heading, if the magnitude of the differential rate of change is greater than the maximum expected drift for the gyroscope.