How Accurate Is GPS?

Have you been asking yourself how accurate is GPS? It's common knowledge that GPS or the Global Positioning System is one of the best ways to know your exact location at any point in time.

GPS works by receiving unique signals from at least three satellites at any given point. The signal from each satellite helps in calculating the distance of the GPS unit from these satellites, which in turn helps to determine its longitude, latitude and altitude. However, is this data entirely accurate or are there factors which affect how accurate is GPS?

There are a number of things which can affect the accuracy of the GPS unit. These include natural barriers, atmospheric conditions, radio noise and even the position of the satellite.

Frequency disturbances or even static interferences can enhance the radio noise. This can cause an error in the accuracy by about 10 meters or less. Sometimes, an error of 30 meters can be caused by natural or man-made barriers between the receiver and satellite. These barriers include buildings and mountains. Maximum accuracy can be only achieved when the GPS unit and satellite are in a direct line of sight.

With times, the GPS technology has been developed to surmount these barriers like clouds, mountains and buildings. These technologies include WAAS, DGPS and AGPS which help in determining the exact location despite all the weather and geographical barriers.

AGPS or Assisted Global Positioning System

This system is particularly helpful in case of situations where there is no direct line of sight between the satellite and the GPS unit. In such cases, radio noise causes an error in accuracy.

The AGPS system uses GPS receivers that are located on the cell towers. These receivers communicate via a wireless network. This in turn helps the receiver to receive the correct satellite information through relay. Hence, with AGPS, the battery life is increased since there is no need to calculate the satellite's orbit.

Differential GPS or DGPS

DGPS is another way to enhance the accuracy of the GPS systems especially in case of poor atmospheric conditions. Though this system also relays information via cell tower and other fixed GPS locations, it uses the combined system of two satellites and a fixed GPS location to calculate the exact position, which is then sent to the receiver.

Wide Area Augmentation System or WAAS

This is the latest innovation in GPS technology. This is especially used for air navigation. In this system, WRS or Wide Area Reference Stations are used. These stations are located on the ground and were not accessible to the general public.

Using these stations, the WAAS corrects the GPS transmission errors which are then transmitted to the satellite which in turn transmits these to the handheld unit. This technology helps aircrafts to function in all kinds of weather conditions and has excellent accuracy.

In a nutshell, how accurate is GPS is directly dependent on the system and the technology used. So, next time you buy a GPS, don't get floored by the claims of "excellent accuracy" by the seller. Instead, investigate closely and find out the kind of technology that particular device uses!

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