Furuno GP-150-DUAL - Manual (Page 51)

8-1
8. MENU SETTINGS
8.1 GPS SETUP Menu
Menu description
Fix mode
Two position fixing modes are available: 2D
and 2/3D. The 2D mode provides two
dimensional position fixes (latitude and
longitude only) and is used when three
satellites are in line of sight of the GPS
receiver. The 2/3D mode switches between
two and three dimension position fixing
automatically depending on how many
satellites (three or four) are in line of sight of
the GPS receiver.
ANT Height
Enter the height of the antenna unit above
sea surface (000-999 ft, 000-304 m). The
default setting is 16 ft.
Disable satellite
Every GPS satellite is broadcasting
abnormal satellite number(s) in the Almanac.
Using this information, the GPS receiver
automatically eliminates any malfunctioning
satellite from the GPS satellite schedule.
However, the Almanac sometimes may not
contain this information. You can disable an
inoperative satellite manually on the GPS
SETUP menu.
GPS smoothing, position
When the DOP or receiving condition is
unfavorable, the GPS fix may change greatly,
even if the vessel is dead in water. This
change can be reduced by smoothing the
raw GPS fixes. A setting between 0 and 9 is
available. The higher the setting the more
smoothed the raw data, however too high a
setting slows response time to change in
latitude and longitude. This is especially
noticeable at high ship’s speeds. "0" is the
normal setting; increase the setting if the
GPS fix changes greatly.
GPS smoothing, speed
During position fixing, ship’s velocity (speed
and course) is directly measured by
receiving GPS satellite signals. The raw
velocity data may change randomly
depending on receiving conditions and other
factors. You can reduce this random
variation by increasing the smoothing. Like
with latitude and longitude smoothing, the
higher the speed and course smoothing the
more smoothed the raw data. If the setting is
too high, however, the response to speed
and course change slows. For no smoothing,
enter "0." "5" is suitable for most conditions.
Speed average
Calculation of ETA and TTG, etc. is based on
average ship’s speed over a given period.
The default setting is one minute. Change
the setting if the ETA seems wrong.
RAIM function/RAIM accuracy
RAIM (Receiver Autonomous Integrity
Monitoring) is a diagnostic function which
tests the accuracy of the GPS signal. To use
the RAIM function, enter the range (from
own ship in meters) for which you want to
know position confidence, on the GPS Setup
2/2 menu. The receiver estimates position
confidence using range value and detected
satellite error, and displays (provided the
RAIM function is active) the results as
one of three levels of position confidence, at
the top right-hand corner of the screen. The
three levels are as follows:
SAFE: GPS signal is normal. The positioning
accuracy satisfies the setting value.
CAUTION: RAIM accuracy cannot be
calculated. (Signals from more than five GPS
satellites are necessary.) The positioning
accuracy does not satisfy the setting value.
UNSAFE: GPS signal is abnormal, therefore
the positioning accuracy is not reliable. Note
that the GP-150-DUAL does not exclude
abnormal signals automatically.