10-6

2. Enter satellite number using two digits.
3. Press the [ ] key to display desired option. Each press of the
key deletes item in parentheses (namely, enables the satellite) or
displays DESELECT or FORCED.
4. Press the [ENT] key.
10.4 GPS Smoothing

Latitude and longitude GPS smoothing

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. Note however that too high a setting slows response time to
change in latitude and longitude. This phenomenon is especially no-
ticeable at high ship’s speeds. “0” is the normal setting; increase the
setting if the GPS fix changes greatly.
LATITUDE
RAW POSITION FIX
AFTER SMOOTHING LONG-
ITUDE
Figure 10-4 Latitude and longitude GPS smoothing

Speed and course GPS smoothing

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 setting the more smoothed the raw
data. If the setting is too high, however, the response to speed and
course changes slows. For no smoothing, enter “0”. “5” is suitable
for most conditions.
SPEED (KNOT)
RAW POSITION FIX
AFTER SMOOTHING
COURSE (DEGREE)
TIME
RAW POSITION FIX
AFTER SMOOTHING
TIME
Figure 10-5 Speed and course GPS smoothing