Gnss Antennas - Advanced Navigation Spatial FOG Dual Reference Manual

9.5

GNSS Antennas

The GNSS antennas should be installed level with a clear unobstructed view of the sky
and close to the Spatial FOG 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
FOG Dual's heading to function correctly.
The primary antenna position offset should be configured in the Spatial FOG Dual unit
by using the alignment configuration dialogue in Spatial FOG Manager, see section
11.8.4. The antenna offset is measured from the centre of the Spatial FOG 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 FOG Dual corrects for lever arm velocities.
Incorrect GNSS antenna offset will lead to performance degradation under turning and
angular rotations.
An example installation with axes marked is shown below in Illustration 17 and
Illustration 18. In this installation there would be a positive X antenna offset value, a
negative Y antenna offset value and a negative Z offset value.
Illustration 17: Spatial FOG Dual antenna offset
isometric view
The secondary antenna should be mounted directly behind the primary antenna with
as much separation as possible. The higher the separation the better the orientation
accuracy. See Illustration 19 for example mounting on a car. If it is impractical to
mount the secondary antenna directly behind the primary antenna, it can be mounted
in another position. In this case the secondary antenna offset must be accurately
measured and entered using the dual antenna configuration dialogue in Spatial FOG
Manager, see section 11.8.12.
Spatial FOG Dual Reference Manual
Page 34 of 138
Version 1.0
26/06/2015
Illustration 18: Spatial FOG Dual antenna offset
front view