ComNav Marine 1420 Autopilot System
Using the Navigation Interface
To be safe, learn to use your Navigation
Interface at slow speeds, away from other
vessels.
Turn on the navigation device.
This could be a GPS, plotter, or other
device. Give it time to find its position
accurately and turn off its warning
indicators.
Enter a Waypoint into the navigation
device.
With some navigation devices, it is
necessary to tell them to send information
to the Autopilot. Make sure that it is
sending information in the correct
NMEA 0183 format.
Turn the Autopilot System on & Press
the Nav Key
.
Watch the Control Head. The light above
the Nav Key
should turn on. This
indicates that the Autopilot is receiving
useable NMEA 0183 navigation data.
Your boat will steer towards the
Waypoint, using the information from the
Nav device and from the Compass.
⇒ If the vessel seems to steer away
from the Course line, see Cross
Track Error, next.
If the light above the Nav Key
does not
come on and all the other lights are
flashing, the Autopilot is not receiving any
useable information from your navigation
device.
The first thing to check is your wiring and
your navigation device. Read the
owner’s manual for the navigation
device to make sure that it is sending
out correctly-formatted NMEA 0183
sentences. Also see the Problem
Solving section (page 54).
Cross Track Error
Cross track error is a measure of the
distance your boat has fallen away from
the Course line.
Cross track error is measured as the
length of a line drawn from the Course
line to your position, at right angles to the
Course line.
Cross track error also has a left or right
hand direction. For example: the boat
can be ½ mile to left of the Course line.
Different manufacturers have defined the
direction of the “cross track” differently.
There is no agreement on whether a “left-
hand” cross track error means that the
boat is to the left of the Course line, or
that the line is to the left of the boat.
Because of this, the 1420 Autopilot lets
you change the way it interprets the
direction of cross track error. By pressing
and holding the Nav Key
and pressing the
Green Key
you can change the
interpretation from “normal” to “inverted”,
or vice-versa.
⇒ Your cross track error direction is
correct if the Autopilot is following
the Course line.
⇒ If the Autopilot is steering away
from the Course line while the
Navigation Interface is on, then
the cross track error direction
may be incorrect!
Change the cross track error direction, if
necessary. If the Autopilot begins
steering towards the Course line, you
have solved the problem.
If the problem persists, check that the
light above the Nav Key
is on. If it is off,
see the Problem Solving section. If it is
on, re-check your navigation device’s
settings.
Document PN 29010012 V1.3
50
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