GPS+Receiver

=Global Positioning System (GPS) Receiver= Jackie Van Loantoc

Purpose
//What is the fundamental purpose of the device?// The GPS receiver receives signals from at least four of the 24 satellites that orbit the Earth at all times and calculates its distance from these four satellites. It uses these distances to find its place on the Earth.

Energy
//What energy transformations are seen in its operation?// The GPS receiver is powered by batteries. The electrical energy from the batteries is transformed for many purposes and distributed throughout the device. The energy is used to receive the signals from the satellites and find its place on the map programmed in to the device, and to then light the LCD screen and give voice commands.

These devices also transform electricity to light:
 * IPod Mini
 * IPod Nano
 * IPod Nano-Chromatic
 * Ipod Touch
 * Smart Board
 * Cell Phone
 * Digital Camera
 * Video Camera
 * DVD Player
 * Gameboy Advance SP
 * Gameboy Color

Controls
//What sensors/controls are designed into the device?// The antenna is a sensor in the GPS receiver. It receives signals from the satellites. [|Here is some info on the basics of antennas.] The cell phone also uses an antenna. The thumbstick is a control that allows you to choose and select something on the LCD screen. Some GPS receivers don't use thumbsticks, but touch screen technology instead. There is a sensor over the display screen of a GPS receiver that detects touch. Touching the screen causes a voltage change in the underlying current and is then used to find the location of the touch. The Ipod Touch also has a touch screen sensor. The power button is a control that you use to turn on or off the device.

Materials
//What material(s) are essential to the device?// A quartz clock that is constantly reset is in all of the receivers and atomic clocks are in the 24 satellites. These clocks are in sync with each other. The receiver also uses a built in almanac that tells it where each satellite is at all times.

**Science** //What scientific principle is central to its operation?// 2D Trilateration is a mathematical concept. It uses 3 distances from a single point, and therefore 3 overlapping circles, to find the exact location of the point. In this case, If you know you're standing 10 miles from King of Prussia, 15 miles from Conshohocken, and 12 miles from Bridgeport;you know you're exact location. The point at which the circles around these three locations overlaps (the red dot), shows where you are.



3D trilateration works similarly, but with spheres. Let's imagine that you know you are 5 miles from one satellite. This means that you could be anywhere on a sphere with a 5 mile radius. Then, you know that you're 10 miles from another satellite. The two spheres overlap showing a perfect circle that you could be in. But you need to get more specific. Therefore, you find out that you're 15 miles from a third satellite. The third sphere overlaps with the other two at two points. The fourth sphere is the Earth, which you're on. One of the two points will be on the Earth and the other won't. Now you know at exactly what point you're located on on the Earth! Even though you only need 3 satellites, GPS receivers generally use at least four to be more precise.


 * The digital pattern that both the GPS satellite and receiver transmit at the same time is the [|pseudo-random code] **

Imagine having a sing-a-long with your class. You break into two groups and decide to sing Row Row Row Your Boat. The first group starts singing the first lyric and then 10 seconds later, the second group begins to sing the first lyric. The second group is 10 seconds behind the first group. This analogy can be used to understand how the GPS receiver uses the pseudo-random code to calculate its distance from the satellite. The difference is, in this case the satellite and the receiver begin transmitting the pseudo-random code at the //same// time. However, by the time the satellite's transmission reaches the receiver it is behind the receiver's transmission. The delay between the two codes is the distance between the satellite and the receiver. The code is received in high frequency electromagnetic waves. The GPS uses this to find its distance from the satellites. It then uses these distances to find its place on Earth through 3D trilateration.

When you put your destination into the device, it uses the detailed map stored in its memory to tell you how to get there. The internal maps work in conjunction with the signals received from the satellites. There are many different maps for different purposes; for example trail maps or ski resort maps. The most accurate maps are the USGS Topographic Maps.

The Ipod Nano also stores information. 

Design
//What does a typical device look like?// There are many design varieties of the device. Here's an example of one:

Evolution
//What changes have there been (or could there be) in this device?// Originially, the global positioning system was developed for the U.S. Military, but in the 1980s it was opened up for the public to use. Now, GPS receviers are being adapted to serve a variety of purposes. For example, the [|RoamEO Location System] uses a GPS receiver in dog collars to locate lost dogs. Also, the more advanced GPS receivers have more features and functions. For example, the GO 730 is more expensive, but includes a feature that advises the driver on which lane to switch to on the highway and provides the fastest route based on actual average speeds. A model called the R700t offers a points of interests database and real-time traffic updates,however, it doesn't have the useful text-to-speech function. Some devices include the blue tooth interface feature (Click here to learn about the Bluetooth headset!) and voice command. GPS receivers are always developing for different purposes and more features are being added.

Competitors
//What other devices serve a similar purpose?// Simple paper maps and compasses were used for hundreds of years before GPS receivers.

Partners
//What other devices work in conjunction with this device?// The GPS satellites that rotate the Earth transmit the signals to the receivers.

Siblings
//What other devices use the same scientific principle?// __ These devices also use electrical current: __ 
 * The AM radio receiver also receives electromagnetic signals.**
 * Calculator
 * Cell Phone Touchscreen
 * Computer Keyboard
 * Gameboy Advance SP
 * Gameboy Color
 * Guitar Amplifier

[|Click for a video about GPS receivers!] [|Here's another video!]