One of the two largest global positioning systems via satellite, GPS, can be deployed in a standard format or as an A-GPS service. What are the main features of these technologies?
Facts about GPS
The GPS system is designed to determine the geographic coordinates of an object on which a receiver, navigator or other device capable of receiving GPS signals from a satellite is located. This system assumes the use of the WGS 84 standard, which makes it possible to determine the coordinates of an object on the Earth's surface in three dimensions with an accuracy of 2 cm. In addition, navigation using GPS technology also allows you to measure the speed of a receiver or a similar device moving along the Earth's surface.
Facts about A-GPS
A-GPS technology complements the GPS standard in several ways. First of all, in terms of speeding up the operation of the receivers used in navigation. The fact is that the determination of coordinates only through satellites implies a significant load on the hardware resources of this device. But if you give the receiver the opportunity to use auxiliary sources of determining its location (those used in the A-GPS infrastructure), then it will work much faster.
A GPS-navigator supporting A-GPS technology loads much faster than devices that are not compatible with the corresponding standard. In addition, A-GPS can significantly improve the stability of continuous tracking of the receiver's coordinates: the signal from the satellite is not always stable (especially in urban conditions), and the use of auxiliary channels for determining the location of the navigator in this sense can become a critical condition for the receiver to perform its custom functions.
What specific auxiliary channels for determining the coordinates of the navigator are used when using A-GPS technology? As a rule, this is the mobile Internet using 3G or 4G technology. In some cases, a connection via Wi-Fi is also suitable.
If 3G, 4G or Wi-Fi channels are not available, then the determination of coordinates can be carried out through the base stations of cellular operators. True, this method has a relatively low accuracy - up to 20 meters, often - several hundred meters.
The main difference between GPS and A-GPS is that the first technology involves determining the geographical coordinates of the navigator via satellite, the second - through alternative channels (3G, 4G, Wi-Fi, base stations operators).
A receiver that supports the A-GPS standard usually boots up much faster than a device that supports only “classic” GPS channels. This is possible due to the prompt receipt of coordinates, and in some cases - also updating maps via the Internet or cellular channels.
In addition, a navigator compatible with A-GPS technology can perform its functions in cases where the signal from the satellite is very weak or not at all. Of course, only if the alternative channels for obtaining the coordinates of the device are working.
Having determined what is the difference between GPS and A-GPS, let us fix the conclusions in the table.
|Used to determine the coordinates of the navigator satellites
|Used to determine the coordinates of the navigator 3G, 4G, Wi-Fi channels, towers of cellular operators
|Assumes relatively slow loading of receivers, which lasts about 30 seconds
|Assumes accelerated loading of receivers, the duration of which can be on the order of a couple of seconds
|When used in its pure form, requires a good signal from satellites, otherwise the navigator may stop functioning
|Allows to use additional channels for determining coordinates regardless of the quality of the signal from the satellite