Furuno GD-280, Operator'S Manual

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10-4
Time difference
The GPS uses UTC time. If you would rather use local time enter the time difference between
local time and UTC time. Select Time Difference from the GPS page, enter time difference (use
the key to switch between plus and minus and vice versa), and press the [ENT] key.
Antenna height
Enter the height (in meters) of the GPS antenna above the waterline to get full position accuracy.
Select Antenna Height from the GPS page, enter antenna height, and press the [ENT] key.
Geodetic chart system
The WGS-84 chart system is now the most widely used chart system. However, other chart
systems still exist, thus it is necessary to apply a correction value to the WGS-84 system to
match it to local geodetic chart systems. Select Geodetic Datum from the GPS page, select chart
system used and press the [ENT] key. For Others, enter chart number referring to the Geodetic
Chart List in the on page A-1.
Position offset
The GPS position may be off by some degrees due to signal propagation and other factors. For
example, the GPS shows your boat to be out at sea while in fact it is moored to a pier. In this
case apply an offset to GPS position to correct it. Select the Lat/Long Offset from the GPS page,
enter offset, and press the [ENT] key.
10.1.3 Position fixing criteria
Position-fixing mode
For ships, the position-fixing mode is 2D (default setting) which means position is fixed using
three GPS satellites. For high altitude use, select 2D/3D.
EL mask
Sets the minimum elevation angle a satellite must be located above the horizon in order for the
GPS receiver to fix position. The default setting is 5
°
, which is suitable for most conditions.
Position and speed smoothing
When the DOP or receiving condition is unfavorable, the GPS fix may change greatly, even
when the vessel is dead in water. This change be reduced or smoothed by smoothing the raw
GPS fixes and speed. A setting between 0 and 99 is available, and the default setting is 0 for
position and 5 for speed. The higher the setting the more the smoothed the raw data, however
too high a setting slows response time to change in position.