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DVD Navigation Uses GPS
Although they may be somewhat more advanced than their dashboard-mounted cousins, DVD navigation systems still rely on the once-restricted satellite conglomeration known as the Global Positioning System, or GPS. Developed for military navigation and guidance around the world, GPS relies on dozens of man-made satellites to broadcast fixed-position information to receivers on the ground (which may also include receivers in airplanes, on boats, or in other mobile applications). Because the orbiting satellites constantly broadcast their unique position and identifying information, a GPS receiver with access to at least four satellite feeds can use this information to calculate its exact location through a complex mathematical formula known as triangulation.
Navigation Relies on Maps
Of course, an exact latitude-and-longitude location is not very practical to users who are not intimately familiar with map coordinates. To make the information more useful and more attractive to average users, DVD navigation systems rely on advanced map software to determine a location. Using the coordinates obtained in Section 1, a navigation system can plug the location into a software map to determine its state, city, and even street position to within about 10 feet; by keeping track of how the information changes, the software can also determine whether the GPS receiver is in motion and, if so, the direction in which it is heading.
DVD Maps are Advanced
Once the navigation system interacts with software to determine its location, motion and direction of travel, it can apply this information to advanced mapping software to determine nearby points of interest, or to develop a preferred route of travel to reach a specified destination. Many smaller, portable GPS units have limited storage capacity for such information, and are therefore somewhat limited in the number of restaurants, banks, hospitals, and other points of interest that can be retained in memory. DVD navigation systems, however, rely on maps loaded on Digital Video Disc media for a broad array of interesting locations and destinations. Because DVD media is inherently removable, these systems also offer a distinct advantage over fixed-media devices: The DVDs can be easily and quickly replaced with newer, updated discs that include new businesses, roads and other map features.
