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Motus Reference Manual
Page 41 of 146
Version 1.1
29/11/2019
source, see section 15.2 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 Manual Initialisation dialogue in Motus Manager, see section 12.8.11.
Once navigation initialisation is complete, the position, velocity and acceleration
values will be valid.
11.1.3 Heading Initialisation
Heading initialisation completes once the system has determined a heading. The
conditions required to determine a heading depend upon the heading source being
used, see section 11.4. If magnetic heading is enabled as a heading source the
heading initialisation should complete within 2 seconds after power on. If magnetic
heading is disabled and velocity heading is used as the only heading source, the
heading will initialise once the system travels at a speed of over 1.15 metres/second
for over 5 seconds with a 3D GNSS fix or other source of velocity information. If the
system is hot starting it will remember it's heading from when it was switched off and
use this as the starting heading until another source becomes available.
Until the heading has been initialised, the system will not be able to navigate without
a GNSS fix or other position source and the roll and pitch values will not be able to
reach full accuracy.
11.1.4 Time Initialisation
Time initialisation completes once the system has determined time accurately. For this
to occur the system must receive rough time as well as a 1PPS signal on one of the
GPIO pins. The rough time is typically received from a GNSS receiver when it achieves
a fix. It is also possible to provide an external source of time, see section 15.2 for more
information on external time sources.
Until the time has initialised the values of Unix time and formatted time that Motus
outputs will not be valid and may change.
11.2 Hot Start
Motus is the first GNSS/INS on the market with hot start functionality. This allows
Motus to start inertial navigation within 2 seconds. Motus's hot start is always on and
fully automatic.
A next generation backup battery system within Motus provides the hot start ability for
more than 48 hours without power. When Motus hot starts it assumes that it is in the
same state it was when it lost power and begins navigating from that position. When
the GNSS achieves it's first fix, if this position deviates from the hot start position,
Motus will jump to the new position without causing any side effects to the filter.
Whilst Motus is without power it keeps track of the time accurately to within 1 second
so that the time is immediately valid on a hot start.
Motus's hot start is of particular benefit to vehicle tracking and robotics applications.
The primary benefits are immunity and fast recovery from power failure as well as fast
startup time.