Furuno GP-31, Operator'S Manual

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GPS SETUP menu description
SMOOTH POS (Smoothing position)
When the DOP (Dilution of Precision, the
index for position-fixing accuracy) or receiv-
ing 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. The set-
ting range is from 0 (no smoothing) to 999
seconds. 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 no-
ticeable at high ship’s speeds. “0” is the nor-
mal setting; increase the setting if the GPS
fix changes greatly.
SMOOTH S/C (Smoothing speed/
course)
During position fixing, ship’s velocity (speed
and course) is directly measured by receiv-
ing GPS satellite signals. The raw velocity
data may changes randomly depending on
receiving conditions and other factors. You
can reduce this random variation by in-
creasing 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. The setting range is
from 0 (no smoothing) to 999 seconds.
AVR. SPEED (Speed averaging)
Calculation of ETA and TTG, etc. is based
on average ship's speed over a given pe-
riod. If the period is too long or too short
calculation error will result. Change this
setting if calculation error occurs. The de-
fault setting is one minute. The setting range
is from 0 (no averaging) to 99 minutes.
LAT/LON OFFSET (L/L position offset)
You may apply an offset to latitude and lon-
gitude position generated by the GPS re-
ceiver, to increase position accuracy.
DISABLE SV (Disable satellite)
Every GPS satellite is broadcasting abnor-
mal satellite number(s) in its Almanac,
which contains general orbital data about
all GPS satellites. Using this information,
the GPS receiver automatically eliminates
any malfunctioning satellite from the GPS
satellite schedule. However, the Almanac
sometimes may not contain this informa-
tion. You can disable an inoperative satel-
lite manually. Enter satellite number in two
digits and press the [ENT] key. To restore a
satellite enter “00”.
FIX MODE
Selects position fixing method; 2D or 2/3D.
2D requires three satellites in view of the
GPS receiver; 2/3D requires three or four
satellites in view of the GPS receiver, which-
ever is available. When the 2D mode is
selected, enter the antenna height above
the waterline, to obtain accurate position
data. The default setting is 5 m. The table
provides common feet equivalents.
Meters Feet
Default 5 meters 16.4 feet
3 meters 10 feet
0.3 meters 1 feet