Global Positioning System

The new semester is about to begin. Another 4 months of working late, having fun, and buying coffee whenever possible. To get to one's respective college, university, institute of higher learning, one requires directions. Gone are the days of printing out directions and squinting at them while trying to stay in the same lane.

There is no need to waste paper when you have a GPS device. They have gotten less expensive every year and one can purchase a good device for around $100 that will get him or her from one end of the country to the other, if they so wish.

So how do these things work? How does a GPS device know exactly where you are when you turn it on? Is it tracking your every movement with an invisible radar and sending the information to top secret departments of the government to spy on each and every single citizen?...okay, maybe not.

To put it simply, GPS works on math. Lots and lots of mathematical computations are done every second by the GPS device that you or anyone else might have. There are currently 27
GPS satellites in orbit around the earth at an altitude of 12, 600 miles. Each satellite simply sends down a focussed microwave beam with an algorithm. For the system to function, there has to be at least four satellites in view. When your GPS receiver device picks up the signal, it receives the algorithms from a number of satellites and using a set of equations, and a method called trilateration, the receiver draws a virtual sphere between itself and the satellite. With two or more signals, the virtual spheres intersect in two places. Once in space and the other on earth. The intersection point on earth is the location of the receiver, and thus, you. As more spheres are drawn, the accuracy increases.

By adding more satellites to the equation, you add more spheres and you have greater accuracy of your location. The point of having so many satellites in space orbiting the earth twice a day is to ensure that there will always be a minimum of at least four satellites in view.

So with all those satellites circling around up there, won't they ever crash into one another? That is highly unlikely because there is no wind or interference in space that would make them deviate from their trajectory. Each of which has a very specific path hindering the collision of two or more satellites.

After all, if the satellites collided, that would be a very hefty waste of tax payers money. in recent years, more nations are launching their own versions of the GPS system with their own satellites:
China - COMPASS
European Union - Galileo
Russia - GLONASS
India - IRNSS
Japan - QZSS