24
NAVIGATION INTERFACE
If the autopilot is being interfaced to a
navigation device with several NMEA
outputs, determine the type of output
formats available from its data sheets.
The 1001 autopilot will only support
NMEA 0183 data format and therefore
that format must be selected. If your
navigation device only outputs 0180 or
0182 formats, please consult with
ComNav service personnel to receive
software that will support these older style
formats.
NMEA 0183
The standard baud rate for the 0183 data
format is 4800 baud.
This data format was developed to allow
a number of pieces of electronic
equipment on the vessel to communicate
with each other. It consists of a large
number of data 'sentences' which can
transmit anything from the vessel's water
speed to its present position from one
device to another.
A data sentence consists of a two letter
identification of the sending device,
followed by a three letter identification of
the data sentence, followed by the
corresponding information.
The autopilot can understand a number of
data sentences that contain steering or
speed information. The autopilot ignores
the two letter device identifier, and only
looks for the three letter sentence
identifier, so it will receive information
from any Nav Device which transmits the
correct data sentences.
Some NMEA 0183 data sentences supply
heading from the beginning of track to the
end of the track, which remains constant
until the Nav Device sequences to the
next waypoint. This is the best type of
Heading To Steer information, as it
prevents the wandering which may occur
when the vessel is close to the
destination waypoint as described earlier.
Depending on the type of Nav device and
how it is configured, the autopilot may
sound its alarm and display 'Arr' when the
vessel is close to a waypoint.
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