Madison+and+Breanne

**Madison and Breanne**

GPS stands for Global Positioning System. They get their information from satellites. All GPS satellites synchronize operations so that these repeating signals, moving at the speed of light, arrive at a GPS receiver at slightly different times because some satellites are farther away than others. The distance to the GPS satellites can be determined by estimating the amount of time it takes for their signals to reach the receiver. When the receiver estimates the distance to at least four GPS satellites, it can calculate its position in three dimensions. GPS operations depend on a very accurate time reference, which is provided by atomic clocks at the U.S. Naval Observatory. Each GPS satellite has atomic clocks on board. Tomtom Ease is from $88 to $120 dollars. The screen size is 3.5. It has spoken street names, preloaded maps of US, Canada, and Puerto Rico and also historic traffic data. It’s easy to use. The preloaded maps cover more than 6.5 million miles of road ways in the US. Have a 3-D view, and also a touch screen. The Tomtom Ease is not water proof. We also research the Magellan SE4. The Magellan SE4 is from $100 to $120. The Magellan SE4 has a widescreen, text-to speech and has maps to 48 states. You also get multi-destination routing, and about a three hour battery life. It has a touch screen it will to you to your destination fast and easy. The Magellan SE4 has a search that helps you find upcoming gas stations, restaurants, hotels and more. Last we researched Cydle T43H. The Cydle T43H is from $175 to $180. The Cydle T43H has HD radio. So you can tune in to your favorite radio station anytime. It tells you your current speed, your current location, the current time, the distance to your destination, distance to the next turn, time to destination, speed limit, next street, and you can zoom in and zoom out. Its has 4.3 inch screen. It has 16 gigabytes of memory. It will display the speed limit on major roads. The Cydle T43H will tell you is you are 5 miles per hour over the limit. It has Internet service with it. TomTom EASE Magellan SE4Cydle T43H

For this exercise, you'll need to dust off some simple skills you learned in geometry. Start by imagining a "distance sphere" (in three dimensions) surrounding a GPS satellite. Points on the surface of the sphere are all the same distance from the satellite that's located exactly at the center. This process works by finding the intersection of your //distances// from three or more satellites. Thus, describing it as "trilateration" is actually better than "triangulation", but neither term seems precisely correct from a technical standpoint.
 * Type || Cost || Features ||
 * Tomtom EASE || $88-$120 || touch screen ||
 * Magellan SE4 || $100-$120 || touch screen ||
 * Cydle T43H || $175-$180 || no touch screen ||
 * knowing distance from one satellite places you somewhere on a spherical surface that's centered around the satellite
 * knowing distances from two satellites places you somewhere along a circle that's between the two satellites (defined by the intersection of their "distance spheres")
 * distances from three satellites usually intersect at two points, and if you're not flying around, one of these points will be on Earth's surface
 * distances from four or more GPS satellites will intersect at just one point