Seiwa Si-Tex Vector 3D GPS User Manual
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Chapter 2: Installation
Mounting Orientation
The 3D outputs heading, pitch, and roll readings regardless of the orientation of the antennas. However, the
relation of the antennas to the boat’s axis determines whether you will need to enter a heading, pitch, or roll
bias. The primary antenna is used for positioning and the primary and secondary antennas, working in
conjunction, output heading, pitch, and roll values.
Note: Regardless of which mounting orientation you use, the 3D provides the ability to output the heave of
the vessel. This output is available via the $GPHEV message.
Parallel Orientation: The most common installation is to orient the 3D parallel to, and along the centerline
of, the axis of the boat. This provides a true heading. In this orientation:
•
If you use a gyrocompass, you can enter a heading bias in the 3D to calibrate the physical heading
to the true heading of the vessel.
•
You may need to adjust the pitch/roll output to calibrate the measurement if the Vector is not
installed in a horizontal plane.
Perpendicular Orientation: You can also install the antennas so they are oriented perpendicular to the
centerline of the boat’s axis. In this orientation:
•
You will need to enter a heading bias of +90° if the primary antenna is on the starboard side of the
boat and -90° if the primary antenna is on the port side of the boat.
•
You will need to configure the receiver to specify the GPS antennas are measuring the roll axis
using $JATT,ROLL,YES.
•
You will need to enter a roll bias to properly output the pitch and roll values.
•
You may need to adjust the pitch/roll output to calibrate the measurement if the Vector is not
installed in a horizontal plane.
Figure 2-2 and Figure 2-3 provide mounting orientation examples
.
Forward
motion
Recessed arrow
located on
bottom of
enclosure
Figure 2-2: Recommended orientation and resulting signs of HPR values