System and Method for Performing a Background Calibration for a Magnetometer
A method and system are provided for performing a background calibration of a magnetometer. The method comprises obtaining a plurality of magnetometer readings; applying an active set of calibration parameters to the plurality of magnetometer readings to obtain a plurality of values; applying a new set of calibration parameters to the plurality of magnetometer readings to obtain a plurality of further values; applying an active set of calibration parameters to the plurality of magnetometer readings to obtain a plurality of further values; and replacing the active set of calibration parameters with the new set of calibration parameters when a quality of the plurality of values is higher than a quality of the further values.
1 . A method of calibrating a magnetometer on a mobile device, the method comprising:
obtaining a plurality of magnetometer readings;
applying an active set of calibration parameters to the plurality of magnetometer readings to obtain a plurality of values;
applying a new set of calibration parameters to the plurality of magnetometer readings to obtain a plurality of further values; and
replacing the active set of calibration parameters with the new set of calibration parameters when a quality of the plurality of further values is higher than a quality of the plurality of values.
2 . The method according to claim 1 , further comprising, before replacing the active set of calibration parameters:
performing a quality check of the plurality of values and the plurality of further values; and
comparing the quality of the plurality of values to the quality of the plurality of further values.
3 . The method according to claim 1 , wherein the new set of calibration parameters is generated using a background calibration.
4 . The method according to claim 3 , wherein the background calibration fails if the new set of calibration parameters is determined to be of poorer quality than the active set of calibration parameters.
5 . The method according to claim 1 , wherein the active set of calibration parameters were obtained using a foreground calibration.
6 . The method according to claim 2 , wherein the quality check comprises applying at least one test to the plurality of values and applying at least one test to the plurality of further values.
7 . The method according to claim 6 , wherein the at least one test comprises at least one of comparing the plurality of values to expected values associated with a location estimate for the mobile device; and determining if the plurality of values are within predetermined acceptable ranges or limits associated with the magnetometer.
8 . The method according to claim 1 , wherein the new set of calibration parameters comprises a gain parameter, an inter-axis misalignment parameter, and a constant bias parameter.
9 . A computer readable medium comprising computer executable instructions for calibrating a magnetometer on a mobile device, the computer executable instructions comprising instructions for:
obtaining a plurality of magnetometer readings;
applying an active set of calibration parameters to the plurality of magnetometer readings to obtain a plurality of values;
applying a new set of calibration parameters to the plurality of magnetometer readings to obtain a plurality of further values; and
replacing the active set of calibration parameters with the new set of calibration parameters when a quality of the plurality of further values is higher than a quality of the plurality of values.
10 . The computer readable medium according to claim 9 , further comprising instructions for, before replacing the active set of calibration parameters:
performing a quality check of the plurality of values and the plurality of further values; and
comparing the quality of the plurality of values to the quality of the plurality of further values.
11 . The computer readable medium according to claim 9 , wherein the new set of calibration parameters is generated using a background calibration.
12 . The computer readable medium according to claim 11 , wherein the background calibration fails if the new set of calibration parameters is determined to be of poorer quality than the active set of calibration parameters.
13 . The computer readable medium according to claim 9 , wherein the active set of calibration parameters were obtained using a foreground calibration.
14 . The computer readable medium according to claim 10 , wherein the quality check comprises applying at least one test to the plurality of values and applying at least one test to the plurality of further values.
15 . The computer readable medium according to claim 14 , wherein the at least one test comprises at least one of comparing the plurality of values to expected values associated with a location estimate for the mobile device; and determining if the plurality of values are within predetermined acceptable ranges or limits associated with the magnetometer.
16 . The computer readable medium according to claim 9 , wherein the new set of calibration parameters comprises a gain parameter, an inter-axis misalignment parameter, and a constant bias parameter.
17 . A mobile device comprising a processor coupled to a memory and a magnetometer, the memory comprising computer executable instructions for calibrating the magnetometer, the computer executable instructions comprising instructions for:
obtaining a plurality of magnetometer readings;
applying an active set of calibration parameters to the plurality of magnetometer readings to obtain a plurality of values;
applying a new set of calibration parameters to the plurality of magnetometer readings to obtain a plurality of further values; and
replacing the active set of calibration parameters with the new set of calibration parameters when a quality of the plurality of further values is higher than a quality of the plurality of values.
18 . The mobile device according to claim 17 , further comprising instructions for, before replacing the active set of calibration parameters:
performing a quality check of the plurality of values and the plurality of further values; and
comparing the quality of the plurality of values to the quality of the plurality of further values.
19 . The mobile device according to claim 17 , wherein the new set of calibration parameters is generated using a background calibration.
20 . The mobile device according to claim 19 , wherein the background calibration fails if the new set of calibration parameters is determined to be of poorer quality than the active set of calibration parameters.
21 . The mobile device according to claim 17 , wherein the active set of calibration parameters were obtained using a foreground calibration.
22 . The mobile device according to claim 17 , wherein the quality check comprises applying at least one test to the plurality of values and applying at least one test to the plurality of further values.
23 . The mobile device according to claim 22 , wherein the at least one test comprises at least one of comparing the plurality of values to expected values associated with a location estimate for the mobile device; and determining if the plurality of values are within predetermined acceptable ranges or limits associated with the magnetometer.
24 . The mobile device according to claim 17 , wherein the new set of calibration parameters comprises a gain parameter, an inter-axis misalignment parameter, and a constant bias.