ComNav Vector G2 Installation & Operation Manual Download

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ComNav G2 & G2B Installation & Operation

Document PN 29010093 V1.5

- 46 -

16 December 2016

Supplemental Sensors

Integrated inside the G2’s enclosure, on the main printed circuit board, are three sensors.  An
accelerometer, which measures the tilt of the G2’s enclosure; a solid-state gyro, which
measures the rate of turn, and a magnetometer that may be used to measure the rate of turn
and provide heading guidance.
There are ambiguities associated with the differential phase measurements, and knowing
where to look, can help to eliminate some of the ambiguity.
All sensors act to reduce the heading search even further, which improves heading start-up
and reacquisition times, and also improve the reliability & accuracy of selecting the correct
heading solution, by eliminating other possible but erroneous solutions.
The tilt sensor is factory calibrated.
The gyro and the magnetometer together can provide an accurate substitute heading for a
short period (depending on the Roll and Pitch motions of the vessel), during instances of
momentary obstruction of GPS satellite signals at either antenna; this may occur, for
example, when passing close to high vertical walls, or underneath bridges.
When such obstructions occur, the gyro and magnetometer are automatically used to provide
an alternate source of heading, accurate to within 1.5°, for up to 1 minutes.  Ideally, the gyro
and magnetometer based heading will see the system through to reacquisition.
If the outage lasts longer than 1 minute, the gyro is deemed to have drifted too far and the G2
will begin outputting NULL fields in the heading output sentences, which in turn will typically
cause a “lost heading” alarm on navigation devices.
Normal heading output will return automatically once satellite signals are re-acquired.
As well, the gyro helps improve and smooth (filter) the heading and rate of turn data output by
the G2.

Operation in NMEA 0183 environment

Once the G2 has successfully acquired a sufficient number of GNSS signals, of high enough
quality, it begins to generate navigational data – position, heading, speed and so on.
It’s up to you what you do with that data, of course!
The G2 is configured at the factory with a specific set of output data settings … enabled
output data “sentences”, update rates and Baud rates. All those are described in this section.
The suggested standard wiring diagrams (see Figure 14 and Figure

) are based on that

factory-default output configuration. But you may change the G2’s configuration as required,
and even wire it differently than shown in the standard diagrams.

Output Ports

Typically, the user of a G2 wants it to output certain navigational data, updated at rates that
are suitable for the other equipment connected to the G2, and for what the overall
“navigation” system is supposed to be doing.
As well, the “bit rate” (i.e., Baud rate) at which the G2’s two output ports are transmitting data
(& receiving data, if necessary) must match the device(s) to which each is connected.
The G2’s 3 output ports – Port 1, 2 and 3 – allow for different sets of navigation data to be
output from the G2. Each port can be configured with its own combination of enabled output
data sentences, sentence update rates, and Baud rate.

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For example: when a ComNav autopilot is being used with the G2, heading and
speed from the G2 are needed by the autopilot, in order for it to be able to steer the
vessel

safely

on the course that the user wants to follow.

– All ComNav autopilots need heading to be updated at a rate of about 10 Hz or

more; any slower causes the autopilot’s steering control algorithm to respond too