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following:
VBW
Vessel Speed relative to water from Dual
Doppler Speed Log.
VHW
Vessel Heading and Water Speed
VTG
Vessel Track and Ground Speed
CROSS TRACK ERROR RESPONSE
The response of the autopilot is set with
the master select switch in the NAV
position.
Press the TURN key, and then the green
ARROW key to select normal indicated
by an 'n' on the right of the display, or
reversed indicated by an 'r' on the right of
the display response to cross track error.
If the setting is incorrect, the vessel will
initially turn to the correct heading, but
then as some cross track error develops,
the vessel will continually turn further and
further away from the correct heading to
the waypoint.
Cross Track Error contains two pieces of
information; the amount of the error, and
the 'sense' of the error (i.e. whether the
vessel is to the Left or the Right of the line
between the beginning and ending
waypoints).
The NMEA National Marine Electronics
Association has specified how the cross
track error should be identified (i.e. a
(L)eft indicator in the data sentence
means the vessel should steer to the left
and a (R)ight indicator meaning the
opposite).
However, some manufacturers have used
the (L)eft indicator to mean that the
vessel is to the left of the line, which
means the vessel should steer to the
right, and the (R)ight indicator to mean
the opposite.
Because of this confusion, the response
of the autopilot to cross track error can be
switched from 'Normal', meaning the
vessel will respond normally to the sense
of the cross track error, to 'Reversed',
meaning the vessel will respond the
opposite way in response to the same
information.
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