Updated 26 May, 2012, 4:18 pm IST

No More Wrong Turns, Go GPS Go!

08 Sep, 2010, 4:15 pm IST | by Kamakshi S

When you're lost and don't speak the language, your best friend can be your little GPS device.

Have you ever been lost while on your way to a wedding or an important appointment? You may have the aid of Google Maps on your cell phone, but despite that, you'll still find yourself relying on local guidance for help. However, in a diverse country like Inidia, being in another city and looking for landmarks can be difficult as roads, buildings etc. don't always go by the same names as the language is different. Even if Hindi is somewhat universal, if you're a guy, asking directions can be a strict no-no, so you'll need to rely on technology, a man's best friend. That's where GPS comes in, and that can be a women's best friend too. � �

Here's a quick look at what GPS and A-GPS is all about before we go any further.

Working of a GPS System
A Global Positioning System uses 27 satellites (24 active, plus three as backup in case of failures) to enable a person to pin-point his current location. The calculation to ascertain the location is based on a simple arithmetic theory known as trilateration. Since Earth is a sphere, each satellite covers a specific part of the sphere and hovers and revolves with it. An intersection of three such spheres closest to the GPS device’s location is done, and the location is thus identified. This technique is known as 3D trilateration. To gather the requesting device’s current location and provide accurate response, the GPS receiver requires two vital details, i.e. the location of at least three satellites above it and the distance between the device and each of those satellites. These details are usually provided using low-frequency radio signals.

Hence more expensive GPS devices tend to have multiple sensors for better quality reception. This information is relayed back to the receiver device, via radio waves or other communication techniques.

Working of An A-GPS System
GPS devices can plot absolute directions based on your current position or they can give you directions through a map device irrespective of your current position. Thus a good GPS system with high-sensors can cost you quite a lot. As a step further, A-GPS technology helps to overcome issues of poor reception. Suited for mobile devices, A-GPS takes assistance from GPRS and, at times, the service provider network information, to pin-point the current location accurately. Moreover, the amount of CPU and programming required for a GPS phone is reduced by diverting most of the work to the assistance server instead.

A typical A-GPS enabled cell phone uses a GPRS or other such Internet based data connection to build a contact with the assistance server for A-GPS. This exercise usually is a bit slow if you are connecting with the server for the first time. As this technique does not take into account the cell phone service provider network completely, you only pay the GPRS usage charges and nothing else. The only down-side to this technology is that an A-GPS server cannot utilize any of the three standby satellites available for GPS connections.