GPS

GPS systems
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What do the Satellites do? __** The satellites send radio signals down to Earth. The signals contain information about each satellite, including the precise time. The GPS receiver, which can be either a hand held unit, a vehicle-based receiver or a static ground station receives and decodes that signal. These receivers were, until the early 1980s, only available to military personnel. The system was designed and implemented by the Department of Defense in order to coordinate attacks with large numbers of troops. While the system is still in use worldwide, manufacturers such as Garmin and Magellan rose to the top of the industry by offering quality civilian units. While the civilian units are very accurate, often to within just a few feet, the military models, which sometimes use multiple antennas are accurate to within inches. The time code included in the signal is compared to the precise time kept in the ground unit. By comparing the data contained in the transmitted signal to that stored in the unit, a location can be determined to within 10 to 20 meters. With a secondary antenna, or another receiver slaved to the first, accuracy can be reduced to inches. As long as the GPS receiver can contact at least three satellites on the GPS network, a position fix can be determined; of course the system is designed so that at least three satellites are above the horizon at any given time. The more GPS satellites that a receiver can detect, the greater the accuracy. Often, as many as 8 or 10 satellites can be detected, and the civilian units can offer near one meter accuracy. __ Cost __ Purchasing a GPS based on price can be a major disadvantage. If you purchase a "bargain GPS," you will get what you pay for, and features such as traffic and up-to-date maps could be lacking. __ Directions __ Turn-by-turn directions are not available on every type of GPS device. Some will give very little advanced notice before an upcoming turn. __ Accuracy __ Maps on GPS devices are not updated in real time for all models. This means that it is possible a GPS device will direct you onto a road that is closed or no longer exists. It could also miss new roads and businesses. __Battery Life__ GPS units that are not plugged into a power source, and rely on batteries, which can drain quickly. This can increase the cost of owning a GPS unit significantly. Sound alarms are losing their relevance. GPS-navigation opened a new era in the field of security systems. Today, many cars are in the base set are special devices that can be used as a defense of his car against theft. Enabled tracking system that the owner is always aware of where his car - with the attempt of unauthorized access to a mobile phone or any other specified by motorists, comes the message and call that a car tried to open. The need to use exactly this system is now more appreciated by the owners of other cars that already know what the repair Auto Mazda or any other machine after an unsuccessful attempt to lock the mechanism as a result of theft. If the theft was fortunate to find a car today and not be a problem, if it is installed GPS-navigation. The signal from the transmitter in the car will be supplied to the satellite and transmitted to the appropriate receiver. If the owner plugged your phone number to the system, it will instantly receive a message about the whereabouts of his car. Of course, no law enforcement officials to return the car is impossible, but unlike in the days when the stolen car were one of hundreds, perhaps thousands, today there is a real chance to find their vehicle.
 * __ How Does it Know Where You Are? __**
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