System, method and apparatus of a motion sensing stack

A system comprising a motion sensing stack, said motion sensing stack comprising at least four magnetometers and an IMU (inertial measurement unit), the IMU comprising an accelerometer and a gyroscope;

• wherein at least one magnetometer is in a different plane from at least three other magnetometers;
• wherein the system is implemented with a plurality of dies, a first die comprising three magnetometers, a second die comprising a processor, and a third die comprising a magnetometer, the accelerometer and gyroscope, and a package, wherein said package contains said dies ordered in a plurality of stacked layers;
• wherein said at least four magnetometers are calibrated according to a calibration process, said calibration process comprising:
• moving each magnetometer according to a defined movement;
• receiving magnetometer data during said defined movement;
• comparing magnetometer data for a plurality of magnetometers;
• and calibrating a frame for said plurality of magnetometers according to said comparing;
• wherein said comparing magnetometer data for said plurality of magnetometers comprises determining a point cloud distribution for each magnetometer;
• calculating Eigen vectors for principal directions of said point cloud distribution;
• and comparing said Eigen vectors;
• wherein said calibrating comprises applying a rotation to said Eigen vectors;
• wherein said plurality of magnetometers are further calibrated according to data from said gyroscope and said accelerometer;
• and further comprising a processor for executing a plurality of instructions, comprising:
• determining a differential gradient between said at least one magnetometer in a different plane and said at least three other magnetometers;
• calculating an azimuth according to said differential gradient;
• and fusing said azimuth, an orientation calculation from said gyroscope, and a tilt calculation from said accelerometer to determine a position to further calibrate said plurality of magnetometers.