Motus Reference Manual
Page 43 of 146
Version 1.1
29/11/2019
where possible through installation location. To compensate for static magnetic
interference, magnetic calibration should be performed any time Motus's installation
changes.
Motus 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
Motus 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 heavily reinforced concrete. It is important to note that for Motus's dynamic
magnetic compensation filter to operate correctly, Motus needs to get a GNSS fix at
least once every time it is moved more than 50km. Each time Motus moves more than
50km the new position is stored permanently and allows Motus to update it's world
magnetic model values.
There are three types of magnetic calibration available, these are 2D calibration, 3D
calibration and automatic calibration. 2D calibration involves one level rotation about
the Z axis and is designed for vehicles that cannot easily or safely be turned upside
down, such as full size cars, planes and boats. 3D calibration involves rotating through
all orientations and is designed for vehicles that can easily and safely be rotated
upside down, such as model size vehicles. 3D calibration offers slightly better
performance and is recommended where possible. Automatic magnetic calibration
continuously and automatically calibrates for static magnetic interference while the
unit is in operation. It is not as accurate as the 2D or 3D calibration, however it is very
convenient for applications where Motus needs to just work without user intervention.
Please note that if Motus is going to be used in a vehicle, the calibration should be
performed while Motus is mounted in and fixed to that vehicle. This means that the
whole vehicle must be moved to perform the calibration. The calibration needs to be
performed in an area away from sources of magnetic interference. For example if
Motus is installed in a car, the calibration should not involve driving over steel drains
or reinforced concrete etc. If Motus is being calibrated to operate standalone, the
calibration should not be done on a desk with a steel frame.
11.5.1
2D Magnetic Calibration
The following procedure should be used to perform a 2D magnetic calibration.
11.5.1.1
Using the Motus Manager Software
1. The unit should be powered on while the vehicle is in a level orientation and
kept stationary.
2. After power on wait 5 minutes for the temperature and filter to stabilise.
3. Open Motus Manager and connect to the device. Ensure that the device has
either a GNSS fix or the position has been manually entered in the Manual
Initialisation window before proceeding.
4. In the Tools menu, open Magnetic Calibration. Click the 2D Calibration button.
See section 12.9.1.
5. Whilst keeping as level as possible, rotate the vehicle in either direction through
one and a quarter full rotations. In a car this can be achieved by driving in one
and a quarter circles.
