Electronic compass and compensation of large magnetic errors for operation over all orientations

A method of compensating an electronic compass to obtain accurate azimuth data for any orientation of the electronic compass despite the presence of perturbing magnetic effects, the method comprising:

• obtaining, for each of a plurality of combinations of orientations and azimuths, a measured magnetic field vector HMEAS representing magnetic field strength along three axes and a measured gravity vector GMEAS representing gravitational field strength along three axes;
• calculating, as a function of the plurality of measured magnetic field vectors HMEAS and the plurality of measured gravity vectors GMEAS, a matrix compensation coefficient LE and a vector compensation coefficient HPE by solving a system of equations;
• storing a plurality of component values of the matrix compensation coefficient LE and of the vector compensation coefficient HPE in a memory associated with the electronic compass;
• subsequently retrieving the plurality of component values of the matrix compensation coefficient LE and of the vector compensation coefficient HPE from the memory;
• obtaining a measured magnetic field vector HMEAS representing magnetic field strength along three axes and a measured gravity vector GMEAS representing gravitational field strength along three axes;
• using the matrix compensation coefficient LE and the vector compensation coefficient HPE to correct measured magnetic field data by applying a formula of the form ĤEARTH≡LE·HMEAS−HPE, where ĤEARTH is the compensated value for the Earth's true magnetic field;
• and
• calculating the azimuth data as a function of the corrected magnetic field data.

An electronic compass arrangement, comprising:

• a three-axis magnetometer, configured to obtain a measured magnetic field vector HMEAS representing magnetic field strength along three axes;
• a three-axis gravity sensor arrangement, configured to obtain a measured gravity vector GMEAS representing gravitational field strength along three axes;
• a microprocessor arrangement, communicatively coupled to the three-axis magnetometer and to the three-axis gravity sensor arrangement and configured to
• use a matrix compensation coefficient LE and a vector compensation coefficient HPE to correct measured magnetic field data by applying a formula of the form ĤEARTH≡LE·HMEAS−HPE, where ĤEARTH is the compensated value for the Earth's true magnetic field, and
• calculate the azimuth data as a function of the corrected magnetic field data;
• and
• a memory, communicatively coupled to the microprocessor arrangement and configured to store the matrix compensation coefficient LE and the vector compensation coefficient HPE.

A microprocessor-readable medium having microprocessor-executable instructions stored thereon, the microprocessor-executable instructions causing a microprocessor to, upon execution of the microprocessor-executable instructions:

• obtain a measured magnetic field vector HMEAS representing magnetic field strength along three axes and a measured gravity vector GMEAS representing gravitational field strength along three axes;
• use a matrix compensation coefficient LE and a vector compensation coefficient HPE to correct measured magnetic field data by applying a formula of the form ĤEARTH≡LE·HMEAS−HPE, where ĤEARTH is the compensated value for the Earth's true magnetic field;
• and
• calculate the azimuth data as a function of the corrected magnetic field data.