Nissan Altima HL32 Hybrid. Manual - part 41

AV-156

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[BOSE AUDIO WITH NAVIGATION]

NAVIGATION SYSTEM

NAVIGATION SYSTEM

System Diagram

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System Description

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NOTE:

Refer to NAVI System Owner's Manual for system operation.

The navigation system periodically calculates the vehicle's current

position according to the following three signals: Travel distance of

the vehicle as determined by the vehicle speed sensor, turning angle

of the vehicle as determined by the gyroscope (angular velocity sen-

sor), and the direction of vehicle travel as determined by the GPS

antenna (GPS information).

The current position of the vehicle is then identified by comparing the

calculated vehicle position with map data read from the map DVD-

ROM, which is stored in the DVD-ROM drive (map-matching), and

indicated on the screen with a current-location mark.

By comparing the vehicle position detection results found by the

GPS and by map-matching, more accurate vehicle position data can

be used.

The current vehicle position will be calculated by detecting the dis-

tance the vehicle moved from the previous calculation point and its

direction.

TRAVEL DISTANCE 

Travel distance calculations are based on the vehicle speed input signal. Therefore, the calculation may

become incorrect as the tires wear down. To prevent this, an automatic distance fine adjustment function has

been adopted.

TRAVEL DIRECTION 

Change in the travel direction of the vehicle is calculated by a gyroscope (angular velocity sensor) and a GPS

antenna (GPS information). As the gyroscope and GPS antenna have both merit and demerit, input signals

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SEL684V

AV

NAVIGATION SYSTEM

AV-157

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from them are prioritized in each situation. However, this order of priority may change in accordance with more

detailed travel conditions so that the travel direction is detected more accurately.

MAP–MATCHING

Map–matching is a function that repositions the vehicle on the road

map when a new location is judged to be the most accurate. This is

done by comparing the current vehicle position, calculated by the

method described in the position detection principle, with the road

map data around the vehicle, read from the map DVD-ROM stored in

the DVD-ROM drive.

Therefore, the vehicle position may not be corrected after the vehicle

is driven over a certain distance or time in which GPS information is

hard to receive. In this case, the current-location mark on the display

must be corrected manually.

CAUTION:

The road map data is based on data stored in the map DVD-

ROM.

• In map-matching, alternative routes to reach the destination will be

shown and prioritized, after the road on which the vehicle is cur-

rently driven has been judged and the current-location mark has

been repositioned.

If there is an error in distance and/or direction, the alternative

routes will be shown in different order of priority, and the wrong

road can be avoided.

If two roads are running in parallel, they are of the same priority.

Therefore, the current-location mark may appear on either of them

alternately, depending on maneuvering of the steering wheel and

configuration of the road.

• Map-matching does not function correctly when the road on which

the vehicle is driving is new and not recorded in the map DVD-

ROM, or when the road pattern stored in the map data and the

actual road pattern are different due to repair.

When driving on a road not present in the map, the map-matching

function may find another road and position the current-location

mark on it. Then, when the correct road is detected, the current-

location mark may leap to it.

• Effective range for comparing the vehicle position and travel direc-

tion calculated by the distance and direction with the road data

read from the map DVD-ROM is limited. Therefore, when there is

an excessive gap between the current vehicle position and the

position on the map, correction by map-matching is not possible.

GPS (GLOBAL POSITIONING SYSTEM)

Type

Advantage

Disadvantage

Gyroscope (angular velocity sensor)

• Can detect the vehicle's turning angle quite 

accurately.

• Direction errors may accumulate when the ve-

hicle is driven for long distances without stop-
ping.

GPS antenna (GPS information)

• Can detect the vehicle's travel direction 

(North/South/East/West).

• Correct direction cannot be detected when the 

vehicle speed is low.

SEL685V

SEL686V

SKIA0613E

AV-158

< FUNCTION DIAGNOSIS >

[BOSE AUDIO WITH NAVIGATION]

NAVIGATION SYSTEM

GPS (Global Positioning System) has been developed and con-

trolled by the US Department of Defense. The system utilizes GPS

satellite (NAVSTAR), sending out radio waves while flying on an orbit

around the earth at the height of approx. 21,000 km (13,000 miles).

The GPS receiver calculates the vehicle's position in three dimen-

sions (latitude/longitude/altitude) according to the time lag of the

radio waves received from four or more GPS satellites (three-dimen-

sional positioning). If radio waves were received only from three

GPS satellites, the GPS receiver calculates the vehicle's position in

two dimensions (latitude/longitude), utilizing the altitude data calcu-

lated previously by using radio waves from four or more GPS satel-

lites (two-dimensional positioning).

Accuracy of the GPS will deteriorate under the following conditions.

• In two-dimensional positioning, the GPS accuracy will deteriorate when the altitude of the vehicle position

changes.

• There may be an error of approximately 10 m (30 ft.) in position detected by three-dimensional positioning,

which is more accurate than two-dimensional positioning. The accuracy can be even lower depending on the

arrangement of the GPS satellites utilized for the positioning.

• Position detection is not possible when the vehicle is in an area where radio waves from the GPS satellite do

not reach, such as in a tunnel, parking lot in a building, and under an elevated highway. Radio waves from

the GPS satellites may not be received when some object is located over the GPS antenna.

• Position correction by GPS is not available while the vehicle is stopped.

SEL526V

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NAVIGATION SYSTEM

AV-159

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Component Parts Location

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