The Difference Betwen GPS and GPRSby John Lister
GPS and GPRS are two separate and unconnected technologies used in cellphone among other devices. GPS is a navigation system that uses satellites to pinpoint the handset's location. GPRS is a technology used for transferring data over a cellphone network.
GPS, or Global Positioning System, is a navigation system for portable devices. It uses a network of satellites surrounding the planet. A compatible device such as a smartphone or a dedicated navigation device has a built-in receiver chip that picks regular up signals from these satellites. Each signal is time-coded so the device can calculate how far away it is from the satellite based on the time the signal takes to arrive. By combining the distances from at least four satellites, the device can calculate its position to within a few feet. It can also cross-reference this with map data to provide navigation such as driving directions.
Not all phones have a GPS receiver, but those that do not may still offer navigation tools. One method is using cellular triangulation which works in a similar way to GPS but using signals from cellphone towers rather than satellites. Because the towers are nearer only three signals are needed to calculate a location, although the resulting location is not as precise. Another method is scanning for nearby Wi-Fi networks and checking their IP address against a database of known networks to find the location. This method is the least reliable and gives even less precise positioning.
GPRS, or General Packet Radio Service, is the standard technology used for data transfers on all but the latest cellphones. It was introduced with the first digital handsets and is also known as 2G, or "Edge" (which is why you may recall seeing an "E" near your signal bars) and continues to be used with handsets supporting faster connections, known as 3G. GPRS is the sister technology of GSM (Global System for Mobile Communications) which is used for voice calls. The key to GPRS is that it breaks data into small pieces known as packets. If there is a problem with the connection, the receiving device can issue a request for the missing packets to be resent without the need to start the entire data transmission again. This mirrors the way data transfers over the Internet.
Newer handsets may run one of two technologies for even faster data transfer, known as 4G. These are called WiMAX (Worldwide Interoperability for Microwave Access) and LTE (Long Term Evolution). They work by using different systems for encoding and transmitting data to make more efficient use of the available bandwidth. 4G services can work for both cellphones and computer devices and aim to give similar performance to wired broadband services in the home. 4G requires a specially built cellphone network which means that as of October 2012 it is much less widely available than GPRS-based services.