Digital compass (also known as electronic compass) is a device that uses geomagnetic measurement principles to determine direction. The three-axis digital compass can provide the carrier's heading angle and attitude angle in real time, and compensate the inclination when the compass tilts to ensure the accuracy of the heading data. With the development of sensor and semiconductor technology, electronic compass has realized miniaturization and low power consumption, and has been widely used in aviation, navigation, land transportation, field exploration and other fields, and is an indispensable part of modern directional navigation system.

The accuracy of the digital compass is determined by the magnetic sensitive element for measuring the geomagnetic field. According to the different working principles of the magnetic sensor used, the commonly used electronic compasses mainly include Hall effect electronic compass, magnetic induction electronic compass, flux-gate electronic compass and magnetoresistive electronic compass. Compared with the above sensors, the magnetoresistive sensor has the advantages of small size, low power consumption and high measurement accuracy, but the disadvantage is poor stability, and the corresponding compensation method needs to be taken to eliminate the influence of external magnetic field and temperature drift, and finally meet the design requirements.

1.Solution of three-axis digital compass attitude angle

The definition of the attitude angle of the digital compass is shown in Figure 1. The magnetic field intensity Hxb, Hyb, and Hzb in the three axes measured by the magnetic sensor are measured under the carrier coordinate system OXbYbZb, and their projections under the navigation coordinate system (geography system) are Hxn, Hyn, and Hzn. N-S represents the Earth's north-south axis, N '-S' represents the geomagnetic north-south axis, and the included angle β is called the magnetic declination Angle. ϕ is the Angle between projected Hny in the geographic coordinate system and the local magnetic meridian in the direction of advance. The pitch angle θ is the angle between the Y-axis of the carrier coordinate system and its projection on the navigation coordinate system, and the roll angle γ is the angle between the X-axis of the carrier coordinate system and its projection on the navigation coordinate system. In this paper, the pitch angle θ and roll Angle γ are calculated from the output of the accelerometer.

The full article: https://www.ericcointernational.com/application/analysis-of-digital-compass-technology-based-on-magnetoresistive-sensor.html
Product information： https://www.ericcointernational.com/digital-compass