Chapter 38 Security, Navigation, and Advanced Driver Assistance Systems 507 Copyright Goodheart-Willcox Co., Inc. starting system. The driver can then start the vehicle’s engine by simply pressing the start button. Navigation Systems A vehicle’s navigation system is an electronic system that helps the driver plan and direct the route to his or her destination. The navigation systems in our cars, on our phones, and on other electronic devices use our nation’s satellite global positioning system (GPS) to dis- play the user’s geographic location. A global positioning system (GPS) uses orbiting satellites to communicate with electromagnetic signals to provide location and time information anywhere near Earth’s surface. These signals are sent and received through a vehicle’s GPS antenna. Once the driver inputs the destination, a road map with the position of the vehicle is shown on the dash monitor display, Figure 38‑5. The navigation system communicates with the satellite system to determine the vehicle’s position. The vehicle’s on-board computer accesses a database of roads and highways to determine multiple routes. GPS may be referred to as a global navigation satellite system (GNSS). Most systems provide other useful information, such as traffic conditions, roadwork, available parking spots, and the number of miles to the destination. Most systems also have verbal output that gives spoken instructions. Advanced Driver Assistance Systems Advanced driver assistance systems (ADAS) use sen- sors, cameras, and the vehicle’s ECM to help prevent collisions and improve driver performance. Many of the ADASs work together and manufacturers install them on the vehicle as a complete package. These assistance systems are also becoming standard on many vehicles. The functions that these systems can perform include the following: • Automatically apply the brakes if an object is detected in the vehicle’s direction of travel. • Warn the driver that he or she is wandering out of his or her lane of traffic. • Steer the vehicle to keep it centered in its lane. • Sound a warning if something is behind the vehicle when backing up. • Adjust the speed of a vehicle to maintain a safe distance between two vehicles. Manufacturers are using ADAS to develop fully autonomous vehicles in which the driver will not have to steer, accelerate, or stop the vehicle. These vehicles use many of the system sensors discussed in the following sections. Sensors Vehicle navigation systems use sensors and cameras to measure distances and detect objects in front of and behind vehicles. Radar, infrared, and ultrasonic proximity sensors are used in navigation systems. Proximity is the distance or nearness that one object is regarding another. Proximity sensors make extremely accurate assessments of the distance of objects around the car. The number of sensors and cameras used on a vehicle depends on the vehicle’s features. Most vehicles use a combination of sensor types that are distributed around the vehicle’s perimeter. See Figure 38‑6. Radar Sensors Radar sensors transmit electromagnetic energy waves that bounce off objects in front of the vehicle and return to the sensor. The system’s computer monitors the time that the waves take to return to the sensor and then uses this information, as well as data from the vehicle speed sensor, to calculate a safe distance between the other car or object and the vehicle. Radar sensors have the longest sensing distance of any type of proximity sensor. Ultrasonic Sensors Ultrasonic sensors use the speed of sound and echo times to calculate the distance of nearby objects. Some sonar sensors make a faint clicking sound. This allows a built-in sensor microphone to measure the amount of time it takes for the sound wave to return to the sensor. Other ultrasonic sensors emit a high frequency sound that bounces off objects near the sensor. Ultrasonic and radar sensors are the two most often used for Warning A driver should not rely exclusively on driver assistance systems. A driver should always be aware of his or her surroundings, always look over his or her shoulders to check blind spots, and use the vehicle’s mirrors. Andrey_Popov/Shutterstock.com Figure 38-5. Large display screens are mounted in the center of the dash where the driver can see and reach the controls. The driver can clearly see the route and location of his or her car on the screen.