8.4 Heading Sources
There are several different heading sources available for Boreas. The heading sources can be configured using
the Filter Options page in the Web UI (see
9.1 Using the Web User Interface
) or in the Manager application
(see
). It is possible to use multiple heading sources and this can provide
performance benefits.
8.4.1 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
9.1.2.12 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,
, or the last good position that is stored in
flash memory.
8.4.2 Dual Antenna Heading
This is the default heading source and provides the most accurate heading while GNSS is available. Dual
antenna heading only works when a good GNSS fix is available to both antennas. It requires a clear view of the
sky with minimal nearby sources of interference or multipath. The greater the antenna separation, the higher
the accuracy (see
6.1.1 Dual Antenna Heading Accuracy
). A minimum antenna separation of 0.5 metres is
required.
Boreas will operate with a single primary antenna connected, but this will prevent dual-antenna heading being
used, although velocity heading will still be possible.
8.4.3 Velocity Heading
Velocity heading works by deriving heading from the direction of velocity and acceleration. Velocity heading
works well with cars, boats, 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 metres/second with a GNSS fix. It is
recommended not to use velocity heading with Boreas unless a dual antenna heading fix is not possible.
Velocity heading is disabled by default.
8.4.4 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
11.4.28 External Heading Packet
or an NMEA message, see
.
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Boreas Reference Manual • Using Boreas
