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.
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.
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.
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).
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.
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.
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).
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.
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.
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 data
Next, the destination is located. Information on destination address, properties (hotel, park, etc.) and other representative features is obtained.
Site information data
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 data
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.
After the route is decided, driving directions commence. Information on buildings and roads along the route is confirmed and displayed.
Road network dataVoice data
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 dataSite information dataBackground dataRivers, shores, railroads, contour lines, administrative limits (cities, towns, etc.)
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.
VICS（Vehicle Information 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.
