Heading observation is one of the most important parameters in an inertial system. Configuring the sensor in an incorrect way can lead to lower performance, so user is advised to read carefully these recommendations.
There are several ways to get the heading from our devices.
- GPS Course
- GPS Accelerometers
- Dual Antenna GPS
In order to choose the best one for your application you will find below how each method works.
MagnetometersIn 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 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
Applications where magnetometers should not be used are mostly automotive or train applications.
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 Course on a plane would get a wrong heading if the plane is drifting due to side wind. GPS course is recommended for automotive applications.
GPS + Accelerometers
Using this mode is only possible when a GPS fix is available. It relies only on the GPS 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.
Some applications that could use this method are motor sports.
Dual Antenna GPSThis method uses two GPS/GNSS antennas to provide both position, velocity and a true Heading angle that is valid, even when stationary.
Using a dual antenna GPS system can be a good solution for several reasons:
- 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
- Most accurate solution
But it is much more sensitive to GPS conditions than single antenna systems. It should be operated in open sky condition for optimal performance.
Marine or airborne survey applications can take advantage of a dual antenna system.