-17-
PRO
PILOT
725 INSTALLATION & SERVICING MANUAL
Installing
Optional
Equipment
The
data
available
for
your
Autopilot
depends
on
the
data
format,
provided
by
the
Navigator,
see
following
table:
Data
available
Data Format
NMEA 0180
NMEA 0182 N M E A 0 1 8 3
Cross
Track
Error
ü
ü
ü
Alarm
Condition
ü
ü
ü
Heading
to
Waypoint
ü
ü
Waypoint
Number
ü
Waypoint Arrival
ü
ü
Note:
Some implementations of 0183 do not output Waypoint
number or Heading to Waypoint.
In order to get full use of the interface facility from your
equipment, it is important to understand the principles of
control used. It would of course be very simple to use the
heading to the next waypoint calculated by the navigator.
However, this would be a dangerous method to use when in
the proximity of land as a stray tidal offset could put the vessel
in a position when it will run aground.
The use of Cross Track Error to control the autopilot heading
enables the vessel to be held on track to the next waypoint. The
autopilot is actually controlled by its own compass output and
the Cross Track Error information is used to calculate the Trim
required to keep your craft on track.
When the waypoint is reached (provided the navigator is
programmed for the next waypoint) Cross Track Error would not
be sufficient information to turn the vessel on to the next track.
To do this it is necessary for the navigator to output the heading
to the next waypoint and indicate that a new waypoint has
