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Tell me about it! How does the car navigation system work?

Many people now use car navigation systems.
Navigation systems are now equipped with various functions, and using such system makes it possible to enjoy safer and more relaxed driving…
Let us explain here some things people think they know, but surprisingly may not, about how car navigation systems work.

How does the car navigation system know a car's location?

Car navigation systems receive signals from satellites and identify the vehicle's position and direction by combining that data with information obtained from various onboard sensors.

  1. Receive signals from satellites and detect the vehicle's location.
    GPS antenna, GPS receiver
  2. Detect the vehicle's direction.
    Direction sensor
  3. Detect the vehicle's travel distance.
    Speed sensor
  4. Car navigation system screen.
    Display
  5. Map database
  6. Check information from the antenna and sensors against the map database and show the results on the display using the car navigation system's control circuitry.
    Navigation computer

1.GPS antenna and GPS receiver

The Global Positioning System (GPS) is a means for detecting position information by making civilian use of satellites originally launched for military purposes by the United States. Today, most car navigation systems are based on GPS position information. To detect GPS position information, a system must be able to receive signals from at least three satellites. In car navigation systems, the GPS antenna and GPS receiver serve to receive signals from these satellites.

2.Direction sensor (gyro-sensor)

Although the GPS antenna allows the detection of the vehicle's position on a map, it cannot determine the vehicle's direction of travel. Car navigation systems use a direction sensor (gyro-sensor) to determine the vehicle's orientation and direction of rotation. The direction sensor (gyro-sensor) contains an oscillating element and calculates the vehicle's direction of rotation and orientation by detecting changes in the element's oscillation triggered by changes in the vehicle's orientation. The car navigation system displays the vehicle's orientation on its screen based on the signal from this direction sensor (gyro-sensor).

3.Speed sensor

Although the system can verify the vehicle's position using GPS data, it may be unable to refresh the position while driving through long tunnels or between tall buildings since it must be able to receive signals from at least three satellites to do so. Car navigation systems use the signal from a speed sensor to determine travel distance, enabling them to refresh the vehicle's position under such circumstances.

4.Display

The display presents a variety of information provided by the car navigation system, including map information, city guide information, the vehicle's current position, and the time. The screen can also be used as a TV screen, and touch screens that allow users to control the system and enter data using the screen have become common recently.

5.Map database

The map database stores a variety of information provided by the car navigation system, including map information, city guide information, and audio data. The system displays the vehicle's current position on the screen by comparing information from the GPS antenna and onboard sensors to information in the map database. Map databases are currently available on a range of media, including CD-ROM, DVD-ROM, and state-of-the-art hard disk drives (HDDs).

6.Navigation computer

The navigation computer is the brain of the car navigation system. It compares information from the GPS antenna and onboard sensors to information in the map database, calculates the vehicle's current position and time/distance to the destination, and shows the results on the display.

How does the system search for the route to a destination?

Between locating a car's current location and directing a driver to a destination, a car navigation system uses the following four databases to decide the route for the driver.

1. Identification of current locationFirst, the current location is identified.

  • Road network data
  • Current location identification: Details

Initially, the current location is identified and indicated on the map display. At that time, the configurations and the locations of nearby roads, connecting routes between roads, as well as attributes such as one-way streets and intersections are ascertained from the system's database.

Road network dataRoad network data

Road configurations
:Altitude, east longitude, north latitude
Current status of connecting roads
:Connected or not connected
Road attributes
:One-way streets, expressways, road width, etc.

2.Finding and setting the destinationSearches for the destination of the driver.

  • Site information data
  • Finding and setting the destination: Details

Next, the destination is located. Information on destination address, properties (hotel, park, etc.) and other representative features is obtained.

Site information dataSite information data

Properties
:Hotel, golf course, etc.
Address (Number, street, city, prefecture, etc.)
Region (tourist site, natural name of area, telephone number, etc.)
Site attributes
:Name, address, telephone number, etc.
Representative spots at destination
 
Arrival location to reach destination.
:Locations that need to be mentioned; for example, parking lot entrances, etc.

3.Route searchRoute to destination is checked.

  • Road network data
  • Route search: Details

After confirming the current location and the vicinity of the destination, the system confirms the route that connects those two locations. Road connection status,intersections, left/right turn conditions, etc. are determined.

Road network dataRoad network data

Current status of connecting roads
:Connected or not connected
Road cost
:Parameters used to calculate the optimum route (road width, one-way streets, toll roads, driving speed, distance, etc.)
Road-to-road cost
:Presence or absence of traffic lights, right turns, left turns, right/left turn prohibitions, etc.

4.Searching for recommended routeRecommended route is suggested.

  • Searching for recommended route: Details

The system determines various possible routes from the current location to the destination, then verifies the optimum route.

In order to identify the recommended route, the following decisions are made.
Factors such as one-way streets, narrow roads, etc. are recognized as costs in terms of route selection, and the route with the least cost is recommended.

5.Route GuidanceDirections are provided for the selected route

  • Road network data
  • Voice data
  • Route guidance: details

After the route is decided, driving directions commence. Information on buildings and roads along the route is confirmed and displayed.

Road network dataRoad network data

Road configurations
:Altitude, east longitude, north latitude
Current status of connecting roads
:Connected or not connected
Road attributes
:Road width, number of lanes, one-way streets, road classifications, names of train lines, ancillary facilities, etc.
Intersection attributes
:Names, traffic signals, toll booths, etc.
Land marks
:Names, locations, landmarks, etc.
  • * When voice guidance is simultaneously available, information is obtained from the voice data and guidance is provided.

Voice dataVoice data

Guidance voice
:Unique place names, guidance voice, etc.

6.Map displayRoute-related information is displayed on the screen.

  • Road network data
  • Site information data
  • Background data
  • Map display: Details

While route directions are being provided, information on the locale through which the car is driving is displayed. In this way, roads, buildings, topographical features, etc., along the way are identified.

Road network dataRoad network data

Road configurations
:Altitude, east longitude, north latitude
Road attributes
:Road width, number of lanes, one-way streets, road classifications, names of train lines, ancillary facilities, etc.

Site information dataSite information data

Target features
Place names
Names of natural areas, etc.
:Facilities, building shapes, names, markings

Background dataBackground data

Rivers, shores, railroads, contour lines, administrative limits (cities, towns, etc.)

How is traffic congestion determined?

The car navigation system can confirm which roads are congested on the basis of the information received from various organizations concerning accidents, road construction, etc.

What is VICS?

VICS(Vehicle Information and Communication System)is a road traffic information communication system that provides drivers with real-time traffic information.
It is possible to verify road traffic congestion conditions, parking lot occupancy conditions, etc., beforehand.

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