GPS Navigators

How Do GPS Navigators Work?

GPS navigators are devices that collect radio signals from a network of satellites to provide you with real-time, instantly updated information about your current location. These units may focus on automotive, maritime or aeronautical use, or they may be handheld units for hikers and outdoor enthusiasts, but they all use the same system to provide information. As long as your GPS navigator has unblocked access to the sky, it can guide you to your next destination.

Satellites

The key to the GPS system is a network of satellites orbiting the Earth. These satellites, maintained by the United States Air Force, travel in carefully monitored orbits in order to provide each region on earth as much coverage as possible. There are at least 24 active satellites at any given time, with extras for redundancy purpose. Generally between four and nine satellites cover any point on the globe at any moment. As long as a GPS navigator can pick up signals from at least four satellites, it can provide accurate positional data, but more signals can provide an even more precise reading.

How it Work?

When you activate your GPS navigator, it searches the sky for signals. Each satellite broadcasts a steady stream of information giving its current location and the time of the broadcast’s origin, and since radio waves travel at a set speed, the navigator can use that data to pinpoint exactly how far it is from each satellite. Once the navigator has distance readings from multiple satellites, it can plot those distances to identify its location in three-dimensional space to within a few meters. The navigator can then compare that point to its internal map database to provide you with information about your area, and give you the ability to navigate to another point on the map with accurate directions.

Maintenance

Most of the maintenance of the GPS network is completely transparent to the end-user, but it is vital in keeping the system running and providing accurate data. The US Air Force tracks each satellite carefully, comparing its actual orbit to its planned path through the sky, and tracking stations note any deviations. Small orbital inaccuracies simply require adjustment to the satellite’s positional signal, but if one of the craft fails entirely, it can affect the accuracy of GPS readings in the affected region. To keep the network functioning at peak efficiency, the Air Force maintains extra satellites in orbit, and launches new craft to replace old or damaged satellites as needed.

Problems

One common GPS problem is a reflected signal. If you are near a mountain or a large building, the signal from a satellite may reflect off its surface, providing your navigator with more than one reading from the same satellite. However, since these reflected signals take longer to arrive, the navigator can compare them with other signals to calculate which one is correct. In canyons or other areas with multiple reflections, however, this can hamper the accuracy of your navigator until you reach a clearer area.