Filter Initialisation
There are four different levels of filter initialisation on GNSS Compass. These are orientation, navigation, heading and time.
The initialisation of each can be monitored by inspecting the
Initialisation Levels
After all four levels of initialisation, the GNSS Compass INS filter takes several minutes to achieve its full accuracy. It is recommended to wait two minutes after initialisation for applications requiring high accuracy.
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, GNSS Compass 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. GNSS Compass 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.
Navigation Initialisation
Once navigation initialisation is complete, the position, velocity and acceleration values will be valid.
Heading Initialisation
Heading initialisation completes once the system has determined a heading using one of its several methods. The conditions required to determine a heading depend upon the heading source being used, see Heading Sources. If velocity heading is enabled and the vehicle is moving, this will be very fast. If the system hot-starts, the last known heading value will be used. However, in order for the Heading Filter to initialise, the system must have a valid heading source.
Until the heading has been initialised, the system will not be able to navigate without a GNSS fix, and the roll and pitch values will not reach full accuracy.
Time Initialisation
Time initialisation completes once the system has determined time accurately. For this to occur the system must receive rough time.
Until the time has initialised, the Unix or formatted time that GNSS Compass outputs will be flagged as invalid.