Dual magnetometer calibration

1. A magnetic sensor comprising:

a magneto-impedance (MI) magnetometer;

a magneto-resistive (MR) magnetometer;

a temperature sensor;

non-transitory storage configured to store a temperature correction database that provides temperature-calibration parameters for the MI magnetometer and an MI-MR measurement pair database; and

a processor in communication with the non-transitory storage, the MI magnetometer, the MR magnetometer, and the temperature sensor, the processor programmed to:

receive a first magnetic reading from the MI magnetometer;

receive a temperature from the temperature sensor;

determine if the temperature is represented in the temperature correction database;

in response to a determination that the temperature is represented in the temperature correction database:

apply the temperature-calibration parameters from the temperature correction database to the first magnetic reading to provide a first temperature-calibrated magnetic reading; and

output the first temperature-calibrated magnetic reading;

in response to a determination that the temperature is not represented in the temperature correction database:

receive a second magnetic reading from the MR magnetometer;

analyze the MI-MR measurement pair database to determine at least one temperature calibration parameter for the MI magnetometer;

apply the at least one temperature calibration parameter to the first magnetic reading to provide a second temperature-calibrated magnetic reading;

store the at least one temperature calibration parameter in the MI-MR measurement pair database; and

output the second temperature-calibrated magnetic reading.

2. The magnetic sensor of claim 1 , wherein the MR magnetometer comprises a tunneling MR (TMR) magnetometer.

3. The magnetic sensor of claim 1 , wherein the temperature sensor comprises a first temperature associated with the MI magnetometer and a second temperature sensor associated with the MR magnetometer.

4. The magnetic sensor of claim 1 , wherein the magnetic sensor further comprises an accelerometer.

5. The magnetic sensor of claim 1 , wherein the MI magnetometer and the MR magnetometer are disposed in a common package.

6. The magnetic sensor of claim 1 , wherein to analyze the MI-MR measurement pair database, the processor is programmed to:

determine that there is sufficient data in the MI-MR measurement pair database to determine the at least one temperature calibration parameter for the MI magnetometer;

in response to a determination that there is not sufficient data in the MI-MR measurement pair database:

apply MR temperature correction to the second magnetic reading to provide a third temperature-calibrated magnetic reading; and

output the third temperature-calibrated magnetic reading.

7. The magnetic sensor of claim 1 , wherein the processor is further programmed to apply a hard or soft iron calibration.

8. The magnetic sensor of claim 1 , wherein the processor is further programmed to apply an outlier reduction or elimination process to magnetic readings from the MI magnetometer.

9. The magnetic sensor of claim 1 , wherein the processor is further programmed to:

detect a hysteresis event; and

apply a correction to a measurement from the MR magnetometer.

10. The magnetic sensor of claim 1 , wherein the temperature-calibration parameters in the temperature correction database comprise an offset, a gain, or both an offset and a gain.

11. The magnetic sensor of claim 1 , wherein the at least one temperature-calibration parameter comprises an offset, a gain, or both an offset and a gain.

12. A method of calibrating a magnetic sensor comprising a magneto-impedance (MI) magnetometer and a magneto-resistance (MR) magnetometer, the method comprising:

obtaining an MI magnetic reading from the MI magnetometer;

obtaining a temperature representative of the MI magnetometer;

determining whether a temperature calibration is available for the MI magnetometer at the temperature;

in response to determining that a temperature calibration is available, outputting a temperature-calibrated MI magnetic reading;

in response to determining that a temperature calibration is not available, determining whether a temperature-calibration can be generated at the temperature;

wherein:

in response to determining that a temperature-calibration cannot be generated at the temperature:

obtaining an MR magnetic reading from the MR magnetometer; and

outputting a temperature-calibrated MR magnetic reading; and

in response to determining that a temperature-calibration can be generated at the temperature:

processing accumulated MI and MR sensor readings to generate the temperature calibration; and

applying the temperature calibration to the MI magnetic reading; and

outputting the temperature-calibrated MI magnetic reading.

13. The method of claim 12 , further comprising applying hard or soft iron corrections.

14. The method of claim 12 , further comprising correcting for hysteresis in at least one of the MI magnetometer or the MR magnetometer.

15. A magnetic sensor comprising:

an MI magnetometer;

an MR magnetometer;

a temperature sensor; and

a processor programmed to perform the method of any one of claims 12 to 14 .

16. A navigation system comprising the magnetic sensor of claim 15 .

17. The navigation system of claim 16 , configured for use with a human-propelled cart, a robotic system, or a drone.