Pioneer AVIC-X3 User Manual download pdf (Page 129)

127

AppendixNAVI/AV

To cancel these limitations, insert the DVD Map

Disc to the navigation system.

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 net-

work of satellites orbiting the Earth. Each of the

satellites, which orbit at a height of 21 000 km,

continually broadcasts radio signals giving time

and position information. This ensures that sig-

nals 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 posi-

tioning in three dimensions. But if signal quality

is poor, only two dimensions, latitude and longi-

tude, can be obtained and positioning errors are

somewhat greater.

Positioning by dead reckoning

The 3D Hybrid Sensor in the navigation system

also calculates your position. The current loca-

tion is measured by detecting driving distance

with the speed pulse, the turning direction with

the Gyrosensor and inclination of the road with

the G sensor.

The 3D Hybrid Sensor can even calculate

changes of altitude, and corrects for discrepan-

cies in the distance travelled caused by driving

along winding roads or up slopes. Also, the navi-

gation 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

vehicle is detected or not:

3D hybrid mode

This is active when the speed pulse is detected.

Inclination of a road can be detected.

Simple hybrid mode

When the speed pulse is not detected, position-

ing is performed in this mode. Only horizontal

movement is detected, so it becomes less accu-

rate. Also, when the positioning by GPS is not

available, such as when your vehicle 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 vehicle

model. In some cases, it is impossible to

make a connection to it, and in such a case

we recommend that the ND-PG1 speed pulse

generator (sold separately) be used.

How do GPS and dead reckon-

ing work together?

For maximum accuracy, your navigation system

continually compares GPS data with your esti-

mated position as calculated from the data of 3D

Hybrid Sensor. However, if only the data from the

3D Hybrid Sensor is available for a long period,

positioning errors are gradually compounded

until the estimated position becomes unreliable.

For this reason, whenever GPS signals are availa-

ble, they are matched with the data of the 3D

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