ComNav Vector G2/G2B Installation & Operation Operation
Document PN 29010078 V2.0 - 58 -
DRAFT #3 – 29 May 2009
Customising & Fine-tuning the Configuration
There are a number of situations where you might want to change the Vector G2’s
factory-default configuration settings in ways other than simply enabling or disabling the
specific sentences that your system requires, or changing the update rates of the enabled
sentence(s).
Roll Alignment
One common situation is if you have mounted the G2 athwartships.
In this case, you must tell the G2 that it is mounted that way, by sending it the following
commands:
$JATT,ROLL,YES
and
$JATT,HBIAS,90.0 (if you have mounted the G2 pointing to Port)
or
$JATT,HBIAS,-90.0 (if you have mounted the G2 pointing to Starboard)
The ROLL command tells the G2 that it is pointing athwartships, so that it will output its
RTK-based “pitch/roll” measurement in the “roll” field of the $PSAT,HPR output sentence.
The HBIAS command (you would send only one of the ones above) tells the G2 which
side of the vessel it is pointing to. When it is pointing to Port (see Figure 3), the G2 must
add 90° to its RTK hea
ding computations, in order to get the vessel’s correct heading;
alternatively, when pointing to Starboard 90° must be subtracted from the computed
heading.
Note: the HBIAS command does not affect the RTK-based “pitch/roll”
computation (for the HPR sentence), nor the actual tilt measurement
by the tilt sensor (in the INTLT sentence). These values are always
based on the tilt angle between the Primary & Secondary antennae.
In order to tell the G2 that you have mounted it pointing at the bow:
$JATT,ROLL,NO
$JATT,HBIAS,0
Note: this is the factory-default. You would only need to send these
commands to the G2 if you have been using an athwartships
mounting, and then have re-mounted the G2 in a “parallel to
centreline” orientation.
Biased Alignment(s)
If there is some bias in the alignment of the G2’s enclosure, you will need to tell the G2
what that is. Some examples:
• If the enclosure is mounted pointed at the bow, but at a slight angle (say, 5.5° to
Port): $JATT,HBIAS,5.5.
– For 5.5° to Starboard: $JATT,HBIAS,-5.5.
• If the enclosure is mounted athwartships, but at an angle slightly less than
abeam (say, 81.0° to Port): $JATT,HBIAS,81.0.
– If pointed 81.0° to Starboard: $JATT,HBIAS,-81.0.
• If the enclosure is mounted with a slight tilt (say, 7.5°) from the Primary antenna
to the Secondary antenna: $JATT,PBIAS,-7.5.
– If the tilt is from the Secondary to the Primary antenna: $JATT,PBIAS,7.5.
Note: the PBIAS command only affects the RTK-based “pitch/roll”
computation (for the HPR sentence), not the actual tilt measurement
by the tilt sensor (in the INTLT sentence).
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