Veripos AB-V-MA-00618 User manual

Document
Title:
GNSS Heading Antenna Installation Guide
File Ref.:
AB-V-MA-00618
Rev No:
A2
Page 1
Purpose
The purpose of this guide is to provide technical guidance and best practice
information on GNSS antenna installations specifically when used for GNSS
heading determination. This guide should be used in conjunction with the
Antenna and Coaxial Cable installation guide
Background
GNSS heading systems determine where an object is pointing with respect
to true north on the horizontal plane. GNSS heading is a vector calculation
between two separated GNSS antennas. The calculation is performed at
the range level. As most errors are common for both GNSS antennas, RTK
level accuracy of the vector measurement can be attained.
As with all GNSS measurements satellite visibility is the primary
consideration, however other factors still need to be considered: -
•Antenna separation
•Common satellite visibility
•Height
•Orientation
Antenna Separation
The antenna separation is the distance between the primary and the
auxiliary antennas. The table below is an example of how the specified
GNSS heading accuracy for Veripos Heading receivers improves as the
antenna baseline separation increases.
Antenna Separation
Heading Accuracy (RTK fixed)
1m
0.3 degrees
3m
0.1 degrees
10m
0.03 degrees
If Veripos Technicians are mobilising the system and 3-meter separation
cannot be achieved, this shall be discussed with the customer to advise the
expected accuracy.

Document
Title:
GNSS Heading Antenna Installation Guide
File Ref.:
AB-V-MA-00618
Rev No:
A2
Page 2
Common Satellites Visibility
The heading computation requires common GNSS ranges measurements
so it is important to ensure that both GNSS antenna are tracking as many
common satellites as possible. Both antennas should ideally have the same
satellite visibility, coaxial cable types and cable lengths. The GNSS
antennas should also be of the same make/manufacturer and model.
Height
Install both GNSS antennas at the same height as this will help to ensure
similar satellite visibility and will aid alignment along a known vessel
orientation. The figure below illustrates the effect of vessel roll on GNSS
antenna installed at different heights.
Figure 1 GNSS Antenna Height Mismatch

Document
Title:
GNSS Heading Antenna Installation Guide
File Ref.:
AB-V-MA-00618
Rev No:
A2
Page 3
Orientation
Figure 2 GNSS Antenna Installation
Ideally the baseline between the installed GNSS antenna will be orientated
along the vessel centre line (along ship). If this is not practical the GNSS
antennas should be installed perpendicular to the centreline (across ship).
These two scenarios are illustrated in the figure above.
Calibration values (c-o) should be applied within Survey or DP software.
Avoid storing the calibration factor within the GNSS system if possible.
The heading vector is calculated from the Position GNSS antenna to the
Heading GNSS antenna. In the figure above the System 1 heading is 90
degrees and the system 2 heading is 180 degrees.
Summary
When planning the GNSS heading antenna installations all the above
factors need to be considered. To ensure a good heading measurement
keep GNSS antenna separation at least three metres whilst maintaining
the best possible visibility. Install the GNSS antennas at the same height
and orientate ideally along-ship otherwise across-ship. Calibration should
be applied in DP or Survey systems.