GPS Systems: How Do They Work?

Whenever we have a better understanding of a technology such as GPS systems and how they work, it helps us appreciate that technology and understand its cost.  GPS systems are added – and more frequently, standard – features in the latest cars, PDAs (Personal Data Assistants) and cell phones.  This article will explain in words that the average person can understand how GPS systems work. Full technical details can be found in other articles published on the Net.

GPS for Beginners

Did you know that there are approximately 2500 satellites currently revolving around the earth?  Many of these are global positioning satellites.  Only around 36 actually are operative – the others are retired GPS satellites.  They constantly send a low-power radio signal to Earthly GPS receivers (not the other way around).  In order to detect an exact location, the GPS system evaluates its distance from three of these satellites.

GPS systems satellites are about seventeen feet across when their solar power panels are fully spread out.  Yep, they work on solar power and also have backup batteries installed for use when solar isn’t available.  They are built to last ten years (knock on wood). There is a “senior” satellite that has been functional since 1978.  His task is to tell the newer satellites how tough it was in his time and how much better the new models have it. Yes, I’m joking!

But Seriously

So what is a GPS receiver?  If a device is capable of receiving the signals output by GPS satellites, it can be considered a GPS receiver.  There was in all probability a GPS receiver on that cruise ship you were on last summer, another in the taxicab you needed to the airport last week and then there’s that Navigon 7100 GPS that your boss just bought for his auto.  The current average price tag for a personal GPS unit is about $300.  When you realize that you didn’t have to pay to design, build or launch a gps satellite into orbit, $300 doesn’t appear excessive at all.

It’s the US government who bears the price for constructing the satellites and launching them into space. So you can sit back and relax in your car, understanding that this network of satellites will speedily and dependably direct you to your destination. So the next time you power on your GPS system, you should feel that you have a working knowledge of how GPS works.