Using GPS navigation is becoming as commonplace as looking at a map. In-dash navigation systems are being installed in most new vehicles, portable GPS units are regularly used by hunters and hikers and GPS navigation can be enabled on most smartphones. But how does this technology work? How does that little receiver know where you are? It's actually a fairly simple process; however getting the infrastructure set up was quite the task.
Like most technology, the Global Positioning System (GPS) was originally created for military use and has only recently become available to civilians. The first GPS satellite was actually launched back in 1978. Since that time, they've created a constellation of satellites orbiting the earth. Over 50 satellites have been launched, but only approximately 30 are active. The GPS satellites need to be replaced every 10 years or so.
Each one of these GPS satellites can orbit the globe twice a day. As they travel, they send out a low-power radio signal to the earth below. Your GPS navigation unit receives this signal and measures the time it took for the signal to get from the satellite to the receiver. The arrangement of their orbits ensures that you'll always have a satellite ready to send a signal to your receiver.
A GPS unit needs to be in direct range of at least three satellite signals in order to correctly pinpoint your latitude, longitude and your movement in that space. If you're locked into four satellite signals then your receiver can also calculate altitude. This satellite information is then cross-referenced with the map database provided on the GPS unit.
While the satellites and GPS receiver are able to calculate your latitude, longitude, altitude and movement, it is the map database that names the roads and labels the buildings. It can be truly said that your GPS navigation unit is only as good as your map database. Two of the biggest map database providers are NAVTEQ and Tele Atlas. NAVTEQ is primarily associated with GPS units such as Garmin and Magellan, while Tele Atlas is usually associated with TomTom. There are many differing opinions about which map database provider is best, but as far as we've seen, it's just a matter of personal preference.
If you want a completely accurate signal from your GPS navigation receiver, make sure that you are in an open area where you have a clear view of the sky. You won't be able to see the satellites, but, trust us, they can see you. Since they use a low-power signal, the satellites need a clear path to your receiver. If you're indoors or under heavy tree cover, you're going to have a hard time getting an accurate signal. The signal can also be affected by reflection, whether you're in the middle of some tall buildings or near a high rock face.
GPS navigation is a quick and easy way to get to where you want to go. However, most people take for granted the amount of work it has taken just to have your in-dash navigation system find the nearest gas station. Simple navigation requires multiple orbiting satellites, a long-distance radio signal, precise timing and extensive research for map databases. So give your little GPS unit a pat on the back the next time you use it, it has earned its keep.