Many of the sophisticated control systems of modern automobiles require measurements of the vehicle’s attitude. Commercial GPS attitude systems are the method of choice for measuring attitude in many aircraft and farm vehicle applications, but are not commonly used on automobiles. The prohibitive aspects of commercial GPS attitude systems on a car include their relatively high cost and significant loss of integrity and signal availability in urban road environments.
Modern automobiles are equipped with a variety of control systems that improve passenger safety and comfort. Such systems include anti-lock brakes, differential steering and cruise control. Recently, automotive GPS systems have also been added to many cars for use in positioning purposes, allowing the driver to view his/her position on a map, and receive directions in real time. The advent of GPS receivers in cars has initiated efforts to enhance existing control systems, and to create new ones such as car-following and lane keeping control. Many of these control systems require measurements of the vehicle’s attitude.
Some other kind interesting integrations and functions of automotive GPS system are that the color LCD screens on some automotive navigation systems can also be used to display television broadcasts or DVD movies. A few systems integrate (or communicate) with mobile phones for hands-free talking and SMS messaging (i.e., using Bluetooth or Wi-Fi). Automotive navigation systems can include personal information management for meetings, which can be combined with a traffic and public transport information system.
Having many advantages automotive GPS systems have some of evils also as a number of road accidents have been attributed to misdirection by satnav systems. On May 11, 2007, a driver followed satnav instructions in the dark and her car was hit by a train on a rail crossing that was not shown on the system. In Exton, Hampshire, the County Council erected a sign warning drivers to ignore their “sat nav” system and to take another route, because the street was too narrow for vehicular traffic, and property damage resulted from vehicles getting stuck.
As the automotive GPS system has many types a very interesting type of automotive GPS system is portable GPS system. This type of GPS navigation device is not permanently integrated into the vehicle, having only a simple bracket to mount the device on the surface of the dashboard and powered via the car cigarette lighter. This class of GPS unit does not require professional installation and can typically be used as handheld device, too.
Benefits of this type of GPS unit include low cost as well as the ability to move them easily to other vehicles. Their portability means they are easily stolen if left inside the vehicle but cannot be stolen if the driver takes it with him when he gets out. Furthermore not having a compass, accelerometer or inputs from the vehicle’s speed sensors, means that they cannot navigate as accurately by dead reckoning as some built- in devices when there’s no GPS signal. More modern portable devices such as the TomTom 920 have an inbuilt accelerometer to try to address this.