GPS		COMPUSA'S TOP SELLERS
Garmin Nuvi 255W GPS (Refurbished) Go wide and get peace of mind with nüvi 255W. This affordable, widescreen navigator leads the way with voice-prompted turn-by-turn directions. Only $99.99	Garmin Nuvi 265WT 4.3" GPS, TTS/BT - Refurbished With a 4.3" Wide Screen, the 265WT, navigator is packed with features such as hands-free bluetooth, Text-to-Speech, and it's Traffic ready. Only $129.99	1.  Magellan RoadMate 1412 4.3" 2.  Garmin Nuvi 255W GPS (Refur 3.  Garmin Nuvi 265WT 4.3" GPS, 4.  Garmin Nuvi 1490T Auto GPS ( 5.  Garmin Nuvi 255W GPS 6.  Garmin Nuvi 1690 GPS 7.  Magellan Maestro 5310 GPS ( 8.  Garmin Nuvi 1370T Auto GPS 9.  Magellan RoadMate 1470 GPS 10.  Garmin Nuvi 255 3.5" GPS - R Also Available: Overstock - GPS

TomTom One130S GPS (Refurbished) TomTom One130S GPS - 3.5" Touch Screen Display, Text To Speech, North American Maps (Refurbished) Only $69.99    Garmin Nuvi 255 3.5" GPS - Refurbished Garmin Nuvi 255 GPS - 3.5" Touch Screen, HotFix, Picture Viewer, 3D Map View, North American Maps (Refurbished) Only $84.97    Magellan RoadMate 1430 4.3" TTS, MSN - Refurb Magellan RoadMate 1430 GPS - 4.3" Wide Touchscreen, Text to Speech, US And Canada Maps, MSN (Refurbished) Only $79.99    Motorola TN30 Auto GPS Motorola TN30 Auto GPS - 4.3" Touch Screen, Bluetooth, Text-To-Speech, US/Canada Maps Only $89.99    TomTom XL 325S Auto GPS TomTom XL 325S Auto GPS - 4.3" Touch Screen Display, Widescreen, Preloaded Maps, North America Only $99.99    Magellan Maestro 4250 GPS (Refurbished) Magellan Maestro 4250 GPS - 4.3" Touch Screen Display, 6 Million POI, Text-To-Speech, Bluetooth, Voice Command Capable, North American Maps (Refurbished) Only $109.99    Magellan RoadMate 1430 GPS Magellan RoadMate 1430 GPS - 4.3" Wide Touchscreen, Text to Speech, US and Canada Maps, 3 Months Free Traffic Alerts Only $119.99    Garmin Nuvi 255W GPS Garmin Nuvi 255W GPS - 4.3" Touch Screen Display, 3D Map View, SD Card Slot, HotFix, North American Maps Included Only $159.99    Garmin nuvi 855 GPS Navigation Garmin nuvi 855 GPS Navigation - 4.3" Touch Screen Display, MicroSD Cards, Speaks Street Names, North American Maps Only $199.99    Magellan RoadMate 1470 GPS Magellan RoadMate 1470 GPS - 4.7" Touch Screen Display, Text-To-Speech, Lane Assistant, North America Maps Only $129.99    Magellan Maestro 5310 GPS (Refurbished) Magellan Maestro 5310 GPS - 5.0" Touch Screen, North American Maps, Text-to-Speech, Ultra Thin Design (Refurbished) Only $119.99    Garmin Nuvi 1490T Auto GPS (Refurbished) Garmin Nuvi 1490T Auto GPS - 5" Touch Screen Display, Ultra Thin, Bluetooth, North American Maps (Refurbished) Only $199.99    Garmin Nuvi 250W GPS Navigation Garmin Nuvi 250W GPS Navigation - 4.3" TFT Touchscreen, Picture Viewer, North America Maps Only $129.99    Garmin Nuvi 1300 Auto GPS Garmin Nuvi 1300 Auto GPS - 4.3" Touch Screen Display, MicroSD Card Slot, 48-States/Puerto Rico/Hawaii Only $139.99    Magellan 4350 4.3" GPS Magellan Maestro 4350 GPS Navigation - 4.3" Touch Screen Display, 3D Views, Landmarks, U.S./Canada/Puerto Rico Maps Included Only $269.99    Magellan RoadMate 1212 GPS Magellan RoadMate 1212 GPS - 3.5" Touchscreen, Text to Speech, Maps of North America and Puerto Rico Only $79.99

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Global Positioning System – GPS

At the end of the 1970s, the United States Department of Defense (DoD) conceived a Global Positioning System (GPS), which allowed any element of the military (planes, ships, submarines, tanks, ground forces) to know their position – via the technique of trilateration – precisely and instantaneously, anytime and anywhere on the Earth's surface. The Global Positioning System (GPS) was built to fulfill this task.

In essence, the GPS system is made of a constellation of satellites constantly orbiting the Earth, at an average altitude of 20,000 kms, scattered on six equally spaced orbital planes. As a result, at least three satellites are always visible at any time from any place on the Earth’s surface. Each satellite emits a coded signal containing essential GPS Navigation/GPS Location information, such as its position and the exact timing of the signal emission to Earth. Therefore, only a simple receiver is needed to measure the elapsed time between emission and reception of the signal. The satellite to station distance is deduced from this travel time.

By way of trilateration, three different measurements made on three different satellites provide the three distances needed to determine the three coordinates of the station (GPS systems) position (the location of the receiver): latitude, longitude, and altitude. This type of measurement is known as "pseudo-range" measurement in GPS jargon. Every satellite emits two types of pseudo-ranges: A precise code (P code), which enables a position precision of around 10 meters, and a coarse code (C/A code), which allows a precision of around 100 meters. The precise code is encrypted and restricted to the U.S. military receivers. Civilian applications are based on the pseudo-ranges measurements of the C/A code. Even using the C/A, incredibly precise location positions are still possible for everyday use.

GPS Navigation Systems

There are three main types of GPS devices available for consumer and commercial use: GPS Navigation, GPS Tracking and GPS Location.

GPS Navigation (such as Garmin GPS or Magellan GPS Navigation Systems) is used to help you locate where YOU are right now, and get you from Point A to Point B. There are numerous devices made for GPS Navigation. From hand-held units equipped with a digital compass to navigators that are installed in cars and commercial vehicles, by manufacturers such as Garmin, Magellan, TomTom, Navigon, Sony and more. These are basically mapping systems, which are used as a Personal Navigation Device. Each has very limited recording (tracking) capability and generally do not have the ability to create and upload detailed logs of vehicle travel, though they do often include a digital compass and a chart for general navigation.

Several businesses have already invested in mapping systems to increase productivity by improving route planning. Personal navigation devices, which can be used for geotagging, are also becoming widespread. In conjunction with a digital camera, geotagging allows you to mark the precise location of where your pictures were taken. As for the navigational system itself, it usually comes with a mounting bracket, and provides easy placement onto your dashboard. Once the mounting bracket is firmly secured onto your dashboard and the GPS navigator is turned on, you are then guided to your destination, usually via text-to-speech and voice instructions from the touch screen. Voice instructions allow you to keep your eyes on the road during your trip, while the GPS remains safely secured on the dash.

The navigational system, which is often times Bluetooth-enabled, also provides several Points of Interest throughout your trip, as well as alternative routes to avoid traffic. You can select your Point of Interest via the touch screen. Many are traffic-ready navigators and can detect a congested road up ahead as well. Additionally, you can get a GPS receiver to use with your Bluetooth-enabled portable computer, as well as a software mapping system to provide GPS mapping right on your personal computer, from makers like Deluo and Microsoft.

Used in the automotive industry, GPS Tracking records a log of all vehicle (or personal) activity and travel over an extended period of time. These devices are usually hidden under the dash. GPS Tracking is useful in eliminating time-consuming and poor quality automotive use logs; as well as increase productivity, and accountability, by maximizing business use of your vehicles, while decreasing or eliminating personal use. They are also great to keep track of where kids have been driving to. The best units provide second-by-second tracking for the highest accuracy of position AND speed traveled, while built-in motion sensors only collect data during actual travel, thus allowing for a much longer recording period.

To pin-point the current exact location of your device, GPS Location is used to provide Real-Time positioning of a vehicle or the GPS device, so you know where it is right now. These usually provide minimal tracking capability or none at all, and are not a replacement for GPS Tracking. GPS Location is mostly used for fleet vehicles, emergency location positioning or as an aid in recovery of a vehicle or asset. GPS Location includes a chart and involves "Pinging" the device via satellite or by cell phone, and having it "phone" home with its current position via satellite cellular technology. Therefore, there is a recurring cost for GPS Location that does not usually apply to GPS Tracking.