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Appendix
Appendix
Positioning Technology
The Navigation System accurately measures your current location by combining the positioning by GPS
and by Dead Reckoning.
Positioning by GPS
The Global Positioning System (GPS) uses a network of satellites orbiting the Earth. Each of the satel-
lites, which orbit at a height of 68,900,000 feet (21,000)km, continually broadcasts radio signals giving
time and position information. This ensures that signals from at least three can be picked up from any
open area on the earth’s surface.
The accuracy of the GPS information depends on how good the reception is. When the signals are strong
and reception is good, GPS can determine latitude, longitude, and altitude for accurate positioning in
three dimensions. But if signal quality is poor, only two dimensions, latitude and longitude, can be
obtained and positioning errors are somewhat greater.
Positioning by dead reckoning
The 3D Hybrid Sensor in the main unit also calculates your position. The current location is measured by
detecting driving distance with the speed pulse, the turning direction with the Gyrosensor, and inclina-
tion of the road with the G sensor.
The 3D Hybrid Sensor can even calculate changes of altitude, and corrects for discrepancies in the dis-
tance travelled caused by driving along winding roads or up slopes. Also, the Navigation System learns
the driving conditions and stores information in the memory; thus, as you drive more, the precision of the
positioning becomes more accurate.
The method of positioning changes as follows depending on whether the speed pulse of your car is
detected or not:
3D hybrid mode
This is active when the speed pulse is detected. Inclination of a street can be detected.
Simple hybrid mode
When the speed pulse is not detected, positioning is performed in this mode. Only horizontal movement
is detected, so it becomes less accurate. Also, when the positioning by GPS is not available, such as when
your car enters a long tunnel, the discrepancy between your actual and calculated position may become
bigger.
➲ The speed pulse data comes from the speed sensing circuit. The location of this speed
sensing circuit depends on your car model. In some cases, it is impossible to make a con-
nection to it, and in such a case we recommend that the ND-PG1 speed pulse generator
(sold separately) be used.