Garmin GPSMAP 640 - Manual (Page 46)

40 GPSMAP 620 and GPSMAP 640 Owner’s Manual
Marine Mode: Advanced Configuration
• elevation—set the units of measure for elevation readings
( Feet or Meters ).
• Atmospheric pressure—set the units of measure for
atmospheric ( Millibars or inches of Mercury ) pressure
readings.
Heading—set the reference used in calculating heading
information.
• Auto Mag Var (Automatic Magnetic Variation)—automatically
set the magnetic declination for your location.
• true—set true north as the heading reference.
• Grid—set grid north as the heading reference (000º).
• User Mag Var—set a custom magnetic variation value.
position Format—select the coordinate system in which a given
location reading appears. Do not change the position format unless
you are using a map or chart that specifies a different position
format.
Map Datum—select the coordinate system in which the map is
structured. The default setting is WGS 84. Do not change the map
datum unless you are using a map or chart that specifies a different
position format.
time—change time settings.
• time Format—set the time format (12 hour, 24 hour, or UTC)
for time readings.
• time Zone—set the time zone displayed for time readings.
Configuring Communications Settings
From the Home screen, touch Configure > Communications .
NMeA port 1 or NMeA port 2—select the input/output format
( Garmin Data transfer , NMeA Std. or NMeA High Speed )
for each port to use when connecting your unit to external NMEA
devices, to a computer, or to other Garmin devices.
• Garmin Data transfer—a proprietary data transfer protocol
that is used to interface with Garmin computer programs.
• NMeA Std.—supports the input or output of standard NMEA
0183 data and DSC data for the DPT, MTW, and VHW
sentences.
• NMeA High Speed—supports the input or output of high
speed NMEA 0183 data for most AIS receivers.