Reported December 2008

About GPS: The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the United States Department of Defense. GPS was originally intended for military applications, but in the 1980s, the government made the system available for civilian use. GPS works in any weather condition anywhere in the world, 24 hours a day. GPS satellites circle the earth twice a day in a very precise orbit and transmit signal information to earth. GPS receivers take this information and use a combination of signals to calculate the user's exact location. Essentially, the GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is. Now, with distance measurements from a few more satellites, the receiver can determine the user's position and display it on the unit's electronic map.

What are Pixels?: "Pixel" is short for picture element and represents a single point in a graphic image. Graphics monitors display images by dividing the screen into thousands or millions of pixels, arranged in rows and columns. A megapixel equals one million pixels. Pixels are a measure of digital image quality: the more pixels, the better. The modern digital camera works on the same principle as a conventional camera, but instead of focusing light onto a piece of film, it focuses it onto an image sensor array -- called a charged coupled device (CCD) -- made of tiny light-sensitive diodes that convert light into electrical charges. It turns the fluctuating waves of light (analog data) into bits of digital computer data. The more sensors that are packed onto the CCD's surface, the higher the pixel count, and the higher the resolution of the final image.

The Optical Society of America contributed to the information contained in the TV portion of this report.

If you would like more information, please contact:

Alexei (Alyosha) Efros
Carnegie Mellon University
Pittsburgh, PA 15213
(412) 268-1234
http://www.cmu.edu
efros@cs.cmu.edu

Optical Society of America
Washington, DC 20036-1023
(202) 223-8130
http://www.osa.org
info@osa.org