Screen Size
The screen sizes for these devices are a big reason to choose one over another. There are a few standard screen sizes that you have to choose from 3.5 inches, 4.3 inches, 5 inches or 7 inches. Of course the larger the screen size the more expensive the unit will be. Take for example the Garmin Nuvi 205
which has a 3.5 inch screen, this model retails for around $87 on Amazon compared to the Garmin StreetPilot 7200
boast a gorgeous 7-inch screen for a cool $600!Display Quality
The quality of display is also a very critical feature to consider when buying a GPS device. Some of the older models have monochrome display but most of the more recent units are all color display. Color screens provide more data than their monochrome counterparts but they also use more battery power. Also check to ensure that the device is able to work effectively in various lighting conditions. Some devices are noted as being extremely difficult to read in sunlight even for some of the larger screen which can be pricy. Try viewing the display from different angles because some portable GPS devices are difficult to read from certain angles.
Interface Options
GPS navigation systems for cars have their share of bells and whistles to meet the varied demands of consumers. However, the more feature-rich the devices are the more you will end up paying for them. With that said, there are some features that are pretty standard in recent times. Any GPS system that is worthy of note has street-level maps with voice and text prompted directions while driving. Some of the later devices now have the ability to give deliver text to speech technology which gives you the specific names of streets and not just the generic “Turn right at next intersection” type messages. There are also devices that are able to give you information about points of interests (POI) along the way. The ability to store an address book is also pretty standard. Look for a device with touch-screen controls, automatic rerouting when you swerve off-track, and variable map views, such as 3D and bird's-eye views. As you get into the high-end models, look for advanced lane guidance, voice commands, and real-time traffic and weather alerts, which usually require an annual subscription fee.
Maps
Most GPS devices sold in the US market come equipped with built maps for the lower 48 states. However, depending on your location, make sure that your choose a device that includes the appropriate maps for your region/country. Most manufacturers offer add-on maps, for an additional cost, that expand your device's usable range. Check the manufacturers website to confirm that your location is covered.
Storage
Even though most GPS devices are equipped with built-in maps they might also support removable storage media like Secure Digital or compactFlash memory cards. Mapping data doesn't take up a lot of space and many units even come with a 128MB card.
Accessories
Although most GPS navigation systems for cars are ready to be used out of the box and come with everything you need to get up and running in a matter of minutes. Still, there are a few accessories available that will help you get the most out of your investment, including auxiliary antennas that can be mounted at the base of your windshield to improve signal reception especially in bad weather, and carrying cases to protect your GPS unit when not in use. You can also from a variety of mounting devices, including removable dashboard mounts, motorcycle mounting kits, and low-profile external antenna mounts that adhere to the trunk of your car. You can also purchase additional maps via download or flash memory cards, as well as AC adapters that let you use your portable GPS devices at home or other locations when the built-in battery needs recharging.
