Eclipse AVN5510 Owner's Manual page 160

For reference
3. Glossary
2- and 3-dimensional positioning
Signals do
not intercross
at one point
Vibration gyro sensor
160
Actual
position
Error
Position determined by
2-dimensional measurement
The GPS calculates your position using a 3-point
measurement principle.
Signals received from one satellite are used
determine the distance from that satellite to your
vehicle. Signals received from 3 satellites can
pinpoint your present location.
However, there exists a margin of error in the
GPS satellite and navigation unit resulting in 2-
dimensional positioning using latitudinal and
longitudinal coordinates if signals from only 3
satellites can be received. In such a case,
accuracy is low.
Also, when receiving signals from 4 or more
satellites, 3-dimensional positioning is
effectuated using the latitude, longitude and
altitude of your vehicle. 3-dimensional
positioning is more accurate than 2-dimensional
positioning and the vehicle position display error
margin is reduced.
This sensor electronically detects in which
direction your vehicle turned.
This sensor plays a very important role in the
independent navigation function of this device.