TABLE OF CONTENTS When traveling through unfamiliar areas, vehicle drivers often use paper road maps for route guidance. However, besides being inefficient, searching for a destination using a paper map is unsafe, especially in busy areas. A new technology, incorporating GPS with digital road maps and a computer system, has been developed so that route guidance can be obtained electronically with a touch of a button [20]. Figure 10.12 illustrates this concept.
The role of GPS in this technology is to continuously determine the vehicle's location. In obstructed areas, such as urban canyons and tunnels, GPS is supplemented by a terrestrial system such as the DR system to overcome the GPS signal blockage. As discussed in Section 9.3, DR is a system that uses the vehicle's odometer and a selection from accelerometers, compasses, and gyros to determine the vehicle's direction and distance traveled. This system is accurate only over a short period of time.
The GPS-determined vehicle location is superimposed on an electronic digital road map, containing in its database digital information such as street names and directions, business listings, airports, attractions, and other related information. Once the driver inputs a destination, the built-in computer finds the best route to reach that destination. Such factors as shortest distance and time to destination, one-way roads, illegal turns, and rush-hour restrictions are all considered in the path finding. Some systems allow the drivers to input other factors such as accident avoidance. The driver usually...
