How to choose the best heading method

When no GPS Available

In many applications, the magnetometer is the only reliable way to have a good heading observation.
Using magnetometers for heading observation provides reasonable accuracy as soon as the following conditions are met:

  • A good magnetic calibration is performed, with the sensor installed in its final configuration, in order to map the magnetic field of the current place and any magnetic disturbance around the device.
  • The sensor is placed away from internal magnetic disturbances, such as switching power supplies, power lines, and magnets
  • The sensor is operated in a reasonably good magnetic environment. Short magnetic disturbances can be expected, but long-term magnetic deviations must be avoided

In Automotive Applications

Using this mode is only possible when a GPS/GNSS fix is available. This mode implies to have some speed in order to get a heading estimation. It also requires the vehicle to go forward, without any side slip. For instance, using GPS/GNSS Course on a plane would get a wrong heading if the plane is drifting due to side wind. GPS/GNSS course is recommended for automotive applications.

If High Dynamics

Using this mode is only possible when a GPS/GNSS fix is available. It relies only on the GPS/GNSS and inertial sensors, so there is no mechanical or magnetic constraint here. Heading is well observed when frequent and significant accelerations, such as a turns are performed. When the sensor is operated at constant speed, or stationary, the heading will drift in a pure inertial way, relying only on gyroscopes.

If Low Dynamics

GPS/GNSS True Heading is achieved by using two antennas on the same GPS/GNSS receiver. This method uses two GPS/GNSS antennas to provide position, velocity and a true Heading angle that is valid, even when stationary.
Advantages of dual antenna GNSS:

  • Works when stationary: You don’t need to move or to have accelerations
  • Calibration-free: You don’t need any calibration, and don’t have to worry about magnetic disturbances
  • It is the Most accurate solution

But it is much more sensitive to GPS/GNSS conditions than single antenna systems. It should be operated in open sky condition for optimal performance.

Which Heading Method for Which Conditions?

Conditions Recommended Method
Automotive GPS Course
Marine Dual Antenna GNSS
Subsea Magnetometers
Airborne Dual Antenna GNSS
Racing/Sport GPS + Accelerometers