Navigation Function
The navigation system is composed of the navigation unit, the PCM (vehicle speed signal), the GPS antenna, audio unit and the display unit.
Function Diagram
Vehicle Speed Pulse
The vehicle speed pulse is sent by the PCM. The PCM receives a signal from the countershaft speed sensor, then the processes the signal and transmits it to the speedometer and other systems.
Yaw Rate Sensor
The yaw rate sensor detects the direction change (angular speed) of the vehicle. The sensor is an oscillation gyro built into the navigation unit.
Sensor Element Structure
The sensor element is shaped like a tuning fork, and it consists of the piezoelectric parts, the metal block, and the support pin. There are four piezoelectric parts: one to drive the oscillators, one to monitor and maintain the oscillation at a regular frequency, and two to detect angular velocity. The two oscillators, which have a 90-degree twist in the center, are connected at the bottom by the metal block and supported by the support pin. A detection piezoelectric part is attached to the top of each oscillator. The driving piezoelectric part is attached to the bottom of one oscillator, and the monitoring piezoelectric part is attached to the bottom of the other oscillator.
Oscillation Gyro Principles
The piezoelectric parts have ‘‘electric/mechanical transfer characteristics.'' They bend vertically when voltage is applied to both sides of the parts, and voltage is generated between both sides of the piezoelectric parts when they are bent by an external force. The oscillation gyro functions by utilizing this characteristic of the piezoelectric parts and ‘‘Coriolis force.'' (Coriolis force deflects moving objects as a result of the earth's rotation.) In the oscillation gyro, this force moves the sensor element when angular velocity is applied.
Operation

1. The driving piezoelectric part oscillates the oscillator by repeatedly bending and returning when an AC voltage of 6 kHz is applied to the part. The monitoring-side oscillator resonates because it is connected to the driving-side oscillator by the metal block.

1. The monitoring piezoelectric part bends in proportion to the oscillation and outputs voltage (the monitor signal). The navigation unit control circuit controls the drive signal to stabilize the monitor signal.

1. When the vehicle is stopped, the detecting piezoelectric parts oscillate right and left with the oscillators, but no signal is output because the parts are not bent (no angular force)

1. When the vehicle turns to the right, the sensor element moves in a circular motion with the right oscillator bending forward and the left oscillator bending rearward. The amount of forward/rearward bend varies according to the angular velocity of the vehicle.

1. The detecting piezoelectric parts output voltage (the yaw rate signal) according to the amount of bend. The amount of vehicle direction change is determined by measuring this voltage.

Global Positioning System (GPS)
The global positioning system (GPS) enables the navigation system to determine the current position of the vehicle by utilizing the electric waves transmitted from the satellites in orbit around the earth. The satellites transmit the satellite identification signal, orbit information, transmission time signal, and other information. When the GPS receiver receives the electric waves from three or more satellites simultaneously, it calculates the current position of the vehicle based on the distance to each satellite and the satellite positions on their respective orbits.
Position detection Image with GPS satellite
Precision of GPS
The precision of the GPS varies according to the number of satellites from which electric waves are received and the control condition. The precision is indicated by the GPS mark shown on the upper right of the display.

GPS MARK | NUMBER OF SATELLITES | CONDITION | DESCRIPTION
--- | --- | --- | ---
White GPS icon | 2 or less | Impossible to detect vehicle position | GPS function is normal. The satellite electric waves received by the GPS are too few to detect the vehicle position.
Green GPS icon | 3 | Vehicle position detectable in 2 demensions | The longitude and latitude of the vehicle position can be detected. (Less precise than detection in three dimensions)
Green GPS icon | 4 or more | Vehicle position detectable in 3 dimensions | The longitude, latitude and the altitude of the vehicle position can be detected. (More precise than detection in two dimensions)
Not indicate | ——— | Faulty | The GPS can't be utilized due to a faulty GPS receiver, open in the wire, or other fault.

GPS Antenna
The GPS antenna amplifies and transmits the electronic waves received from the satellites to the GPS receiver.
GPS Receiver
The GPS receiver is built in the navigation unit. It calculates the vehicle position by receiving the signal from the GPS antenna. The vehicle position and signal reception condition is transmitted from the GPS receiver to the navigation control unit to adjust vehicle position.
Navigation Unit
The navigation unit calculates the vehicle position and guides you to the destination. The unit performs map matching correction, GPS correction, and distance tuning. It also controls the menu functions and the DVD-ROM drive. With control of all these items, the navigation unit makes the navigation picture signal, then it transmits the signal to the display unit and audio driving instructions to the audio unit.
Calculation of Vehicle Position
The navigation unit calculates the vehicle position (the driving direction and the current position) by receiving the directional change signals from the yaw rate sensor and the travel distance signals from the PCMs vehicle speed pulse (VSP) signal.
Map Matching Tuning
The map matching tuning is accomplished by indicating the vehicle position on the roads on the map. The map data transmitted from the DVD-ROM is checked against the vehicle position data, and the vehicle position is indicated on the nearest road. Map matching tuning does not occur when the vehicle travels on a road not shown on the map, or when the vehicle position is far away from a road on the map.
GPS Tuning
The GPS tuning is accomplished by indicating the vehicle position as the GPS's vehicle position. The navigation unit compares its calculated vehicle position data with the GPS vehicle position data. If there is large difference between the two, the indicated vehicle position is adjusted to the GPS vehicle position.
Distance Tuning
The distance tuning reduces the difference between the travel distance signal from the VSP and the distance data on the map. The navigation unit compares its calculated vehicle position data with the GPS vehicle position data. The navigation unit then decreases the tuning value when the vehicle position is always ahead of the GPS vehicle position, and it increases the tuning value when the vehicle position is always behind the GPS vehicle position.
Route Calculation Method
The navigation unit can calculate different routes to a selected destination. You have four options:

- Fastest route − minimize the time to the destination
- Shortest route − minimize the distance to the destination
- Minimize motorway − minimize the usage of the motorway as possible
- Minimize toll road − minimize the usage of the toll road include ferry as possible

Audio Guidance
The navigation unit transmits audio driving instructions before entering an intersection or passing a junction.The audio instructions come through the audio unit to front speakers.
DVD-ROM
The map data (including all scale rates) is stored in the DVD-ROM. The map data includes:

- Road distances, road widths, speed limits, traffic regulations, passing time at junction, distances to junctions, and the driving instructions for audio guidance.
- Latitude and longitude GPS.

Glossary
The following is a glossary of terms used pertaining to the Navigation system.

POI | Points of Interest, these are listed under the ‘‘places'' option on the Main Menu
GPS | Global positioning system. A network of 24 communications satellites orbiting the earth.
NAVI | Abbreviation for navigation system.
LCD | Liquid crystal display.
PCM | Powertrain control module.
VSP | Vehicle speed pulse, a travel distance signal supplied by the PCM.
DATABASE | The data (mapping and address information) stored on the DVD-ROM disc and in the navigation system's control unit.
DVD-ROM | Digital video disk read-only memory.
DIGITIZED ROAD | A road that appears on the navigation digitized map screen.
NON-DIGITIZED ROAD | A road that DOES NOT appears on the navigation digitized map screen.
Map Matched(ing) | The navigation system has matched the car to a digitized road segment which is represented when the name of the current road being driven on is indicated on the bottom of the screen in the blue shaded area.

Audio Unit
The audio unit receives the audio driving instructions from the navigation unit and transmits the instructions through the front speakers even when the audio system is in use.
Display Unit
The display unit uses liquid crystal display (LCD). The LCD is a 7-inch-wide, thin film transistor (TFT), stripe type with 336,960 picture elements. The color film and fluorescent light are laid out on the back of the liquid crystal film. The touch sensor on the front of the LCD is an infrared type with 20 vertical and 9 horizontal infrared rays to produce 180 sensing points. The display unit transmits the signal from each operation key and the touch switches to the navigation unit.
Infrared rays