Gnss Antennas - Advanced Navigation Spatial Dual Reference Manual

Spatial Dual Reference Manual
Page 37 of 137
Version 2.3
12/04/2016
other equipment. When wiring the system, the signal ground should be routed with the
primary RS232, auxiliary RS232 and GPIO pins. The power ground should be routed
with the power supply to the power source.
A power supply should be selected that can provide at least the maximum current
calculated from the graph in Illustration 11.
Spatial Dual contains an active protection circuit on the power supply input that
protects the unit from under-voltage, over-voltage and reverse polarity events. The
protection circuit shuts off power and automatically recovers the unit to full operation
once the fault is removed. Take care when running the unit close to its under-voltage
lockout of 8.5 V because small voltage drops can engage the under-voltage shutdown
and potentially oscillate between the on and off state. It is recommended that the unit
is always run at 9.5 V or more to avoid issues associated with this.
9.5

GNSS Antennas

The GNSS antennas should be installed level with a clear unobstructed view of the sky
and close to the Spatial Dual unit where possible. The antennas should be mounted
away from any RF emitters. It is important to have a ground plane (flat conductive
surface such as a piece of plate aluminium) under the antenna with a minimum radius
of 60mm. Correct antenna positioning is very important for Spatial Dual's heading to
function correctly.
The primary antenna position offset should be configured in the Spatial unit by using
the alignment dialogue in Spatial Dual Manager, see section 11.8.5. The antenna
offset is measured from the centre of the Spatial Dual unit to the central base (ARP) of
the antenna in the body frame. It is very important to set the antenna offset
accurately as Spatial Dual corrects for lever arm velocities. Incorrect GNSS antenna
offset will lead to performance degradation under turning and angular rotations.The
antenna offset is measured from the centre of the Spatial unit to the centre of the
antenna in the body frame (X forward, Z down). Please note that as Z is positive down,
mounting the antenna above the Spatial unit will result in a negative Z offset.
An example installation with axes marked is shown below in Illustration 16 and
Illustration 17. In this installation there would be a positive X antenna offset value, a
positive Y antenna offset value and a negative Z offset value.