The Basics: GPS Systems
GPS systems were once the dream of a few science fiction writers. However, these have made the leap from fiction to reality, with the help of a few high-flying satellites that were also just a figment of those same writers' imaginations. In-vehicle navigation systems use a combination of technologies: CD- or DVD-ROM, GPS satellite receivers, internal gyroscopes, and connections to the vehicle speed sensor. Handheld and portable systems typically rely only on GPS data. While these systems are very useful, they have limitations that fully installed systems attempt to overcome.
A GPS (Global Positioning System) receiver uses satellite information to pinpoint your exact location. While this is extremely accurate, many things can cause the system to falter. Trees, tunnels, and tall building can block reception to the satellites (24 satellites are continuously orbiting the planet beaming down information, since at least three satellites are required to accurately find your position.) The gyroscope helps maintain tracking information through turns and twists, and the vehicle speed sensor fills in the gaps when the satellite signal is lost. Location information is then superimposed on the maps stored on discs. The detailed map information is stored on either a CD or DVD, with more than just streets and exit numbers. Many systems have business addresses, so you can enter a name and the system will direct you to it. Others have detailed restaurant, gas station, hotel, shopping, and banking information. On a road trip, you can find out exactly where is the nearest ATM or doughnut shop.
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GPS systems can vary greatly in how and what they do. Some simply tell you where you are. This information can be placed over an extremely detailed map, or it can be a simple latitude/ longitude number. Of course, the more detailed information you have, the more useful a system will be. Other systems can give you turn-by-turn instructions, either visually or audibly. Imagine a pleasant voice telling you that you need to merge ahead, and warning you that the exit ramp is on the other side of the road. Many systems can plan a multiple stop trip--locally or across the country--determining the route with the least mileage or time. You can program them to avoid toll roads, or even to find any scenic routes. Some fully integrated systems can receive local traffic information, to route you around traffic or road construction.
Some systems are self-contained, strictly for navigation only. Others are part of an in-vehicle multimedia setup, utilizing a video monitor can display maps or DVD movies. Another format uses a small single-DIN head unit that combines a radio receiver with the navigation system.
