Heading Sources
There are several different heading sources available for Boreas. The heading sources can be configured using the Filter Options page
North Seeking Gyrocompass Heading
Boreas contains high accuracy gyroscopes allowing it to detect the rotation of Earth to determine North with a high degree of accuracy. Gyrocompass heading is fully automatic and always enabled.
Coarse alignment takes two minutes to complete, during which time some movement is acceptable, however it is best to keep the unit as stationary as possible. The Coarse Heading Alignment Status dialogue in the Web UI provides feedback on the initialisation process.
Fine alignment will occur after coarse alignment is complete. Fine alignment is automatic, and the time taken to reach full accuracy will depend upon operating conditions. Some movement, ideally including 90 degree turns will speed up the time required to reach full accuracy.
For all applications, the gyrocompass heading requires an approximate position that is within a 50 km range. The position can come from the GNSS, Manual Initialisation, or the last good position that is stored in flash memory.
Velocity Heading
Velocity heading works by deriving heading from the direction of velocity and acceleration. Velocity heading works well with cars, fixed wing aircraft and other vehicles that don't move sideways. Velocity heading cannot work for helicopters and other vehicles where the vehicle is pointed somewhere other than the direction of travel. Velocity heading requires a horizontal speed of over 1.15 m/s with a GNSS fix. Velocity heading is disabled by default.
External Heading
This can be used if there is some other way to derive heading that is external to Boreas. The heading must be supplied to Boreas using the External Heading Packet or an NMEA message, see NMEA Input.
External Magnetometers Packet
Heading can derived using the magnetometers of an additional external Advanced Navigation product to input external magnetometer values. See External Magnetometers Packet for details.