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40 GPSMAP 620 and GPSMAP 640 Owner’s Manual
Marine Mode: Advanced Conguration
• 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 species 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 species 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.
Conguring Communications Settings
From the Home screen, touch Congure > 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.