GPS Buying Guide

How it works

The NAVSTAR GPS network was developed by the US Department of Defense in 1973 for defense purposes. It comprises of 30 satellites that orbit the earth and direct you towards your destination in collaboration with a number of ground stations. This phenomenon is known as '3D fix', and is the reason why GPS antennas need a clear sky to work. A regular GPS instrument has a 12-channel receiver, an antenna and a CPU to process the accumulated data, although some of the more recent models have receivers with 40 channels or more, and can track more satellites for better service. The effectiveness of your device depends on how fast can it gather the data, which is why sometimes a GPS system does not work in dense forests, since there is not enough clarity for the antenna to catch a signal.

Cold start

When a GPS is used for the first time, it starts collecting information from the satellite to determine your current location. This is known as a cold start, and the device needs to figure out the current time, the location of the satellites, etc. This process can take a few minutes, depending on the model. Once all the information has been recorded, your GPS would only take a couple of seconds to get going once you are on the road.

Location of the antenna

The effectiveness of a GPS unit depends pretty much on the location of the antenna. In case your GPS is a factory installed unit, the antenna would most probably be integrated into the dashboard in such a way that it would be having a clear view of the sky. There are also quite a few portable models that are placed right above the windshield through a mounting device to give a good view of the sky to the antenna. Further, users can also purchase add-on antennas to keep the receiver near the front seat for better viewing.


There are quite a few options to choose from once you are serious about purchasing a GPS system.

Factory install

A significant number of cars today offer GPS as a standard accessory. The earliest models were CD-ROM based, and had multiple discs to cove the entire area of the US. These were followed by DVD ROM systems, with the whole country's map being stored in one disc. A more recent advancement in factory-installed systems have an in-built hard drive to give more storage space for data to be captured and kept for future reference. Another advantage of hard-drive based systems is that they give faster access compared to their DVD-based counterparts. The latest trend in this regard is the usage of flash memory for storing data. This offers a higher speed than the hard-drive system, and also negates the usage of moving parts, automatically ensuring better response in extreme weather conditions. Coming to the pricing part, factory installed systems are more expensive than portable ones, simply due to the fact that they have a larger screen and better integration with other parts of the car.

Professional installation

If your car isn't already having a GPS system, you can always have one professionally installed after choosing one from the multitude of in-dash systems available. Some of the additional benefits of such systems are iPod integration, multimedia playback from DVD/USB, and so on. The pricing however, can be just as much as a factory installed system. A major attracting factor of a professionally installed GPS system is that it does not have any wires or power adapters, or adhesive mounts that always seem to occupy a lot of space on the dashboard.

Portable Navigation Devices

Portable navigation devices are soon catching up with the more sophisticated in-dash car systems, with the added benefit of being used in multiple vehicles since there are no wires that are to be attached. Some higher end models provide country-wide maps that are stored in their internal flash memory. PNDs basically have a much more user-friendly interface, since there is not need to download maps. It's basically like a plug-and-play hardware for your car. There are vibrant displays, text-to-speech driving directions, and the system can be easily installed and removed with a suction cup mechanism.

Some of the cheaper models require the user to touch a button and select an icon based on their point of interest, followed by pressing the 'Go' button to get directions. They don't have much of the features of the more expensive GPS systems, but are considerably cheaper, and hence, more affordable to serve their basic purpose, i.e., providing GPS navigation.


A majority of the present day smartphones have a built-in GPS receiver or configuration that allows it to function like a full-fledged GPS once the right application has been installed. Alike PNDs, smartphones are very handy and portable, with the user not even having to undergo the process of installation and removal. Further, you can always search on the internet for points of interest, get weather updates, and many more similar features. However, one drawback of using a phone as a GPS is that it has a smaller scree and is not all that safe to look at while driving.



A good display is most certainly the first thing you must be looking at while shopping for a GPS system, particularly in case you don't have a factory installed one. Visibility in all lighting conditions must be checked, since some GPS systems tend to fall flat during the day, and some are too dull to be properly viewed at night. Also make it a point to check if you can view the screen properly from every angle.

A couple of extra add-ons for navigation are also a helpful addition if you are willing to spend that extra buck. Street level maps are definitely a preferred option, as they give you a detailed view of every place there is a provision for in the maps. Often, these also come with voice and text prompts. Further, a GPS could also use the help of a POI database that has the locations of hospitals, airports, shopping dining options, etc., especially if you are treading on unfamiliar grounds. Some GPS systems also come with automatic rerouting feature if you go off course. Some other features are real-time traffic alerts, weather updates, advanced lane guidance, and voice command-compatibility.