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.
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
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
page in the web UI or in
Once navigation initialisation is complete, the position, velocity and acceleration values will be valid.
7.1.3 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
. The default heading source is dual antenna, which will initialise the heading to a high accuracy within
several minutes of power on assuming that both antennas are connected with an unobstructed view of the sky.
The system can be stationary or moving during this initialisation. If velocity heading is enabled and the vehicle is
moving, this will be very fast. If the system is hot-starting then it will use the heading from the heading from
when it was last switched off 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 reach full accuracy.
7.1.4 Time Initialisation
Time initialisation completes once the system has determined time accurately. This occurs as soon as the
GNSS receiver obtains its first fix.
Until the time has initialised, the Unix or formatted time that GNSS Compass outputs will be flagged as invalid.
7.2 Hot Start
Advanced Navigation GNSS/INS devices were the first on the market with hot-start functionality. This hot-start
functionality allows GNSS Compass to start inertial navigation within 500 ms to 1 s, and obtain a GNSS fix in as
little as 2 seconds. The hot-start functionality is always on and fully automatic. See
for details.
A next generation backup battery system within GNSS Compass provides the hot-start ability for more than 48
hours without power. When GNSS Compass 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 could. When
the GNSS receiver achieves its first fix, GNSS Compass will jump to the new position without disturbing the filter.
Whenever GNSS Compass is without power it continues to accurately keep time so that it is immediately valid
for a hot-start.
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