The value of GPS technology to Autonomous navigation systems

True navigation, which provides the user with detailed instructions on how to reach a specific destination, is one of the fastest-growing areas in intelligent vehicle technology. Navigation devices utilize map-matching and best-path algorithms, along with userdefined filtering, to allow the user to choose between the fastest or most direct route to a desired destination. Some systems even allow the user to indicate specific routes to be avoided. The map databases used all provide basic mapping information (streets, major landmarks, etc.), but can also include points of interest and/or helpful location information (restaurants, etc.), depending upon their level of detail and how often they are revised.

 

Autonomous navigation devices range from in-dash units that are small enough to fit into a 1-DIN slot, to multi-component systems with CD-ROM changers and large multi-plane colour displays. The price of these systems can vary from a few hundred dollars to several thousand dollars, depending upon the complexity and capabilities. These systems utilize position information from an integrated GPS tracker , along with map database information provided from a CD-ROM or memory cartridge, to determine the user’s current geographical location on the map. The smaller, in-dash units typically have a limited ability to display the user’s position graphically, instead indicating the current location using a text description, such as the current address or location relative to a near-by landmark. Systems supporting a larger display can graphically indicate the user’s current position superimposed on a map of the surrounding area. Also, because these systems are typically mounted in the dashboard, displacing the existing vehicle entertainment system, many of them include entertainment functionality such as an AM and FM stereo tuner or audio CD player. The more advanced systems with direct interconnections into the vehicle may also include HVAC system controls or other vehicle-specific comfort and convenience controls, although this is usually limited to systems installed by the vehicle manufacturer or dealer. An illustration of the functional blocks of an autonomous navigation system with an integrated GPS receiver can be seen in the picture below.

 

To determine the appropriate travelling instructions with one of these devices, the user enters the desired destination using a menu-driven system via a hardware or software keypad, depending upon the system. Some systems also support voice-based destination entry using basic voice-recognition technology. While these voice-driven systems are becoming more sophisticated, much progress is still necessary to improve them to the point where non-technical users are satisfied with their accuracy and reliability. The methods in which the directions are communicated to the user also depend upon the complexity of the system. Navigation systems with limited displays may use simple graphics combined with text to indicate the directions in a turn-byturn manner. Some systems may combine these graphical turn-by-turn instructions with spoken instructions, using text-to-speech technology. Systems with larger displays can indicate the current position and immediate directions on a map of the immediate area, as well as the desired destination, once it is within the boundaries of the current map being displayed.

 

The value of GPS technology to these systems is obvious. tracking devices for people provides the essential positioning elements of location and speed necessary to make dynamic navigation possible. However, the occasional difficulties in maintaining a GPS position lock, particularly in ‘urban canyon’ areas such as in the downtown districts of big cities, often require the use of additional techniques to maintain the accuracy of the user’s location and movements between position locks. These dead-reckoning techniques, described earlier in this chapter, include the use of internal gyroscopes or accelerometers to track the movement of the vehicle between the times that a solid position fix can be obtained by the GPS receiver. Vehicle speed and direction information, often obtained directly from the vehicle’s internal communication network, can also be used to enhanced deadreckoning capabilities, although the capabilities for the input and processing of this type of data are typically only found in systems installed by the vehicle manufacturers and dealers.

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