Using Certus; Filter Initialisation; Orientation Initialisation; Navigation Initialisation - Advanced Navigation Certus OEM Reference Manual

Certus Reference Manual • Using Certus

7 Using Certus

This section covers the following topics:

7.1 Filter Initialisation

There are four different levels of filter initialisation on Certus. These are orientation, navigation, heading and
time.
The initialisation of each can be monitored by inspecting the 8.1.2.4 Status view in the web UI or 8.2.6 View
Menu in the Certus Manager.
Figure 19: Initialisation Levels
After all four levels of initialisation, the Certus INS filter takes several minutes to achieve its full accuracy. It is
recommended to wait two minutes after initialisation for applications requiring high accuracy.

7.1.1 Orientation Initialisation

Orientation initialisation occurs automatically upon power on and typically completes within seconds. To
determine its orientation it uses the accelerometers to measure the gravity vector. Random accelerations from
environmental sources can disturb this process, which can introduce minor orientation errors that will be
corrected within several seconds. To prevent this, Certus monitors the accelerometers and gyroscopes and
restarts the orientation detection if there are sudden movements. It is however still possible under some
circumstances for it to miss minor movements and start with a small orientation error. Certus will progressively
correct the orientation error over a period of several seconds.
Once orientation initialisation is complete, the roll, pitch and angular velocity values will be valid.

7.1.2 Navigation Initialisation

Navigation initialisation completes once the system has determined a starting absolute position. The most
common method of navigation initialisation is for the system to get a 3D GNSS fix or better. If the system is hot-
starting it will remember its position at the time it was switched off and use this as the starting position. The other
possibility for navigation initialisation is an external position source to be used, see 10.4.25 External Position
Packet for more information. In a situation where a GNSS fix is not available to initialise navigation, it can be
initialised manually by entering a position into the 8.1.3.10 Manual Initialisation page in the web UI or the
8.2.7.12 Manual Initialisation dialogue in the Certus Manager.
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