Magnetic Heading; External Heading; External Magnetometers Packet; Magnetic Calibration - Advanced Navigation Certus OEM Reference Manual

Certus Reference Manual • Using Certus
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.

7.4.3 Magnetic Heading

This is the default heading source and works well in the majority of cases. When using magnetic heading,
magnetic calibration is required every time the static magnetic field around the Certus changes. This can occur,
for example, when moving the mounting location of the unit, or making significant structural changes to the
vehicle that alter the distribution of ferrous materials. The downside of magnetic heading is that prolonged
exposure to dynamic magnetic interference can cause significant heading errors. See

Magnetic Calibration

7.4.4 External Heading

This can be used if there is some other way to derive heading that is external to Certus. The heading must be
supplied to Certus using the
Input.

7.4.5 External Magnetometers Packet

Heading can derived using the magnetometers of an additional external Advanced Navigation product to input
external magnetometer values. See
7.5 Magnetic Calibration
Static magnetic interference is resolved through magnetic calibration. Dynamic magnetic interference is
compensated by a filter algorithm, but should be minimised where possible by selecting the best possible
mounting location or implementing magnetic shielding — see
compensate for static magnetic interference, magnetic calibration should be performed whenever the Certus
mounting location or operation environment changes.
Certus contains a dynamic magnetic compensation filter that is able to mitigate the effects of short term
magnetic interference sources while in operation. For example, if Certus is installed in a car and the car drives
over a large piece of magnetised steel, this will be compensated for. Another example is driving through a
tunnel which is built from reinforced concrete, which can distort the local magnetic field substantially. It is
important to note that for the Certus dynamic magnetic compensation filter to operate correctly, Certus needs to
get a GNSS fix at least once every time it is moved more than 50 km. Each time Certus moves more than 50 km
the new position is stored permanently and allows Certus to update its world magnetic model values.
There are three types of magnetic calibration available: 2D calibration, 3D calibration and automatic calibration.
The three magnetic calibration types and their respective typical applications are described as follows.
2D calibration involves at least one full rotation of the vehicle about the Z-axis and is designed for vehicles
l
that are not intended to travel whilst turned upside down, such as full-sized cars, passenger planes and
boats.
3D calibration involves at least two full rotations of each axis (X, Y and Z) and is designed for vehicles that
l
are intended to be manoeuvred and travel upside down, such as underwater vehicles. 3D calibration
offers slightly better performance, and is recommended where possible. Be mindful that the support
mechanism used to support the vehicle during calibration can influence the results.
v2.4
for further information.
10.4.28 External Heading Packet
10.4.46 External Magnetometers Packet
or an NMEA message, see
6.10 Magnetics
Page 43
6.10 Magnetics
9.6.1.29 NMEA
for details.
for more information. To
2024-12-17
and 7.5