In-Car Navigation Systems Emerge Worldwide
Cars equipped with GPS navigation systems on board use computers and satellite technology to help drivers get to their destinations. As this technology captures the interest of auto manufacturers, electronics companies, and consumers, it is offered in an increasing number of cars. GPS navigation systems are relatively new to American consumers. Overseas, this technology is better established, especially in Japan.

How Do In-Car Navigation Systems Work?
In-car navigation systems utilize GPS with a combination of the following computer hardware and software components:

Map Database: A highly detailed database, including an electronic map of the road structure, is stored on CD-ROM. This database includes a directory of potential travel destinations and businesses in the region.

GPS Receiver: This instrument picks up Global Positioning System (GPS) signals that locate the car's position as it travels.

Monitor: A screen displays electronic maps, system menus, and other information useful to the driver.

CD-ROM Drive: This device reads the database and electronic map features that are stored on CD-ROM.

Central Processing Unit (CPU): The computer's CPU works with information received from each component of the navigation system to determine a driver's location, calculate routes, display the car's position on the monitor, and more.

Navigating with the Security of Information
Car-navigation systems provide continuously updated guidance to drivers. With the security of information, drivers can concentrate on the road and not worry about finding a new destination in an unfamiliar area.

Navigation systems store the equivalent of hundreds of paper maps on CD-ROM. Along with efficiency of targeted database searches, a driver with a navigation system has no need to unfold a paper map. The navigation system automatically searches vast reserves of data to obtain the necessary information.

With voice-prompting technology on board, navigation systems direct drivers step-by-step, so they can keep their eyes on the road. This voice guidance provides an extra measure of safety, as it's not necessary for the driver to glance away from the road at written directions while en route.

As an additional measure of security, the navigation systems use data from the GPS receiver, a gyroscope, and the car's current speed to determine the car's location.

Global Positioning System (GPS) Technology
GPS technology uses signals transmitted by satellites in space. Over two dozen satellites orbit the earth and send signals to receivers on the ground. Originally, these satellites were designed for highly accurate military applications, under the auspices of U.S. Department of Defense. Currently, this system provides valuable position information for civilian applications, as well. In-vehicle navigation systems use civilian grade GPS receivers to obtain the high level of positional accuracy required for navigation.

On-Board Navigation: Autonomous Systems and Hybrid Systems with GPS
Before GPS technology was widely available for vehicles, autonomous navigation systems used a gyroscope and a car's rate of travel to track its position relative to a given starting point. Autonomous navigation systems can generally calculate fairly accurate positions. The accuracy of these calculations declines when a car travels on dirt, sand, or snow and its tires spin more frequently relative to the distance traveled.

Hybrid navigation systems rely on GPS and use the gyroscopes and speed measurements of autonomous systems to optimize performance. An example of how this works is when a car passes through a tunnel and the GPS signals it receives are temporarily blocked. A car equipped with a hybrid system can continue to calculate position using the gyroscope and speed. When the car emerges from the tunnel and reestablishes its connection with the satellite transmissions, GPS data is incorporated into the position calculations again.

Map Matching Function: Placing a Vehicle on the Map
Navigation systems make use of a function called map matching that takes into account slight variations in the quality of GPS transmissions. Through map matching, the system compares positions on the CD-ROM map database to position data received in GPS signals. The map matching function locates the vehicle's position along a single road or within a maze of adjacent roads.

Finding a Destination through Search Functions
Navigation systems make use of a vast database of roadways and destinations. Information in large, metropolitan areas is especially detailed and complete.

To locate a destination, a driver can use the navigation system menu to search by:

• Address
• Point of Interest (POI), organized by category
• Telephone Number