Spatial FOG Reference Manual
Page 42 of 144
Version 2.3
03/05/2018
FOG Manager, see section 11.8.11.
Once navigation initialisation is complete, the position, velocity and acceleration
values will be valid.
10.1.3
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 10.4. If north seeking gyrocompass heading is being used as the sole
heading source the heading initialisation will only complete once the north seeking
alignment procedure has been completed, see section 10.4.1. If velocity heading is
enabled, the heading will also initialise once the system travels at a speed of over 1.15
metres/second for over 5 seconds with a 3D GNSS fix. If the system is hot starting it
will remember it's heading from when it was switched of 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 and the roll and pitch values will not be able to reach full accuracy.
10.1.4
Time Initialisation
Time initialisation completes once the system has determined time accurately. This
occurs as soon as the GNSS receiver obtains it's first fix. It is also possible to provide
an external source of time, see section 12.2 for more information on external time
sources.
Until the time has initialised the values of unix time and formatted time that Spatial
FOG outputs will not be valid and may change.
10.2
Hot Start
Spatial FOG is the first GNSS/INS on the market with hot start functionality. This allows
Spatial FOG to start inertial navigation within 2 seconds and obtain a GNSS fix in as
little as 3 seconds. Spatial FOG's hot start is always on and fully automatic.
A next generation backup battery system within Spatial FOG provides the hot start
ability for more than 24 hours without power. When Spatial FOG hot starts it assumes
that it is in the same state it was when it lost power and begins navigating from that
position. The hot start also provides ephemeris, almanac and time information to the
GNSS receiver which allows it to achieve a fix far more quickly than it otherwise would.
When the GNSS achieves it's first fix, if this position deviates from the hot start
position, Spatial FOG will jump to the new position without causing any side efects to
the filter.
Whilst Spatial FOG 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.
Spatial FOG'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.
