GPS and A-GPS: what is the difference and which is better?


By purchasing a smartphone or tablet, you can find in its characteristics support for GPS and A-GPS. What is this technology with the letter A, and how does it differ from the long-familiar satellite navigation system?

Is there a difference between GPS and A-GPS?

GPS (from the English Global Positioning System – a global positioning system) is a satellite navigation system. It allows you to determine the current location of your gadget on the globe by capturing a signal from a satellite.

And what is A-GPS?In fact, this is not a separate technology, but an add-on to the global navigation system. It adds to it a very important function – triple positioning.

What is triple positioning?

When you turn on the navigation on your phone, it needs to contact the satellite to determine the current location – the so-called “cold start”. Depending on the location of the device, it can take a decent time: from 10-15 seconds to a couple of minutes.

When using new technology, the phone receives coordinates not only from space during a cold start. Data can be taken from the base station of your service provider or, more often, via the Internet – mobile or Wi-Fi.

In a word, wherever you connect first, from there you will get your location. If you are using the towers of a mobile operator, first there may be inaccuracies in the positioning of the device. They are adjusted when the gadget “dials” to the satellite.

What does it give?

One head is good, but three is already a dragon! Positioning according to three different sources allows not only to accelerate the obtaining of coordinates but also to compare them with each other in order to determine the location with an accuracy of several meters.

Another important advantage of the technology is the ability to receive signals in the so-called “dead zones” – tunnels, lowlands, dense forests. One of the three sources of the signal, one way or another, “reaches” the “dead zone”, and the phone receives the coordinates.

Annoying little things

Despite the obvious advantages, the technology has several disadvantages:

  1. Some receivers of this type require the radio to work. If, for example, your tablet does not have a SIM card, that is, the radio module (GSM) is disabled, then you cannot use A-GPS.
  2. Outside the cellular network and without access to the Internet, the function simply does not work.
  3. When using technology, phone or tablet transmits some information via the Internet. Its volume is small – only a few kilobytes. But if you are in roaming, a tangible amount can be debited from your account even for them.

Otherwise, positioning with the letter A is a handy thing. It is not in vain that location determination by three sources is used in children’s watches and dog collars! It is much faster and more accurate than the usual location, and also works where the satellite does not “finish off” – for example, inside reinforced concrete buildings or in the subway.