Megan+and+Jazlyn


 * Today, if you need directions what do you use; a map, MapQuest, or a GPS? Which would be more efficient? Everyone knows how to use a map and most people know how to use the Internet. Well, we're here to tell you how GPS, or Global Positioning Systems, work.**

__ How they work __
 * GPS stands for Global Positioning System. The GPS satellites send signals to the a GPS receiver. Early receivers did not perform well within forested areas or tall buildings, but later receiver designs such as SiRFStarlll, MTK, etc. have overcome this and improved performance and sensitivity markedly. GPS operations depend on a very accurate time reference, which is provided by atomic clocks on board the satellites. Each GPS satellite transmits data that shows its location and the current time. All GPS satellites synchronize operations so that repeating signals are transmitted at the same time. The signals arrive at a GPS receiver at different times because some satellites are farther away from others. The distance to the GPS satellites can be determined by estimating the amount of time it takes for their signals to get to the receivers. When the receiver guesses the distance to at least four GPS satellites, it can calculate its positions in three dimensions. There is always at least 24 GPS satellites on and working at all times, plus extras for spares. A GPS system "knows" the location of the satellites because that information is included in the data. By estimating how far away a satellite is,the receiver also "knows" it is located somewhere on the surface of an imaginary sphere centered at the satellite. Then, it determines the sizes of several spheres, one for each satellite and then it knows the receiver is located where these spheres intersect. The accuracy of a position determined with GPS depends on the type of receiver. Most consumer GPS units have an accuracy of about +/- 10m. The pseudo random code is an I.D. code that identifies which satellite is transmitting information. You can view this number on your GPS unit's satellite information page, the number attached to each signal bar identifies which satellites it's receiving a signal from. Almanac Data is data that describes the orbital courses of the satellites. Every satellite will broadcast almanac data for EVERY satellite. Your GPS receiver uses this data to determine which satellites it expects to see in the local sky. Then, it can determine which satellites it should track. With Almanac Data the receiver can concentrate on those satellites it can see and forget about those that would be out of view. Almanac Data is not precise and can be valid for many month. Ephemeris data is data that tells the GPS receiver where each GPS satellite should be at any time throughout the day.**

__ Examples __

This GPS has 7,000,000 points of interest, premium maps of USA and Canada, it announces the street names, and it includes EastPort mount. The screen is also anti-glare, even in direct sunlight. Another plus is that it has a 2 hour battery life. TomTom also has a feature called "text to speech". It has a 3.5 inch touchscreen.
 * __TomTom ONE 130S __**

__**Garmin Nuivi295w **__ The Nuivi295W is one of the best GPS. It has TFT widescreen of 3.55. It has a 3.5 inch screen. A keyboard is programmed into it. The screen is good to view maps. An antic glare finish is on it when you are outside and it is a sunny day. It wifi is really good. It speaks the street names and traffic data. It has a calendar to store all your appoint meant and meetings. It is about $224.99 or more depend on where you by it. **__Magellan eXplorist 610__** The eXplorist 610 is waterproof and it has a 3.2 mega-pixel camera, microphone, and speakers. In this GPS, you can see 3-D perspective view and it includes a 3 inch touchscreen and button controls. One HUGE plus is it has 15 hours of battery life! It comes with a preloaded World Edition Map. The price is