GPS Buying Guide

Portability is Key
First, the portable units come in a range of sizes. The critical factor is really the screen size and programming keypads that accommodate an adult finger. The larger models measure about seven inches (measured diagonally), but at that size and weight, their portability is compromised.


The beauty of a portable unit is obvious. You can move them from one car to another, take them along on bike rides, or on long walks through new towns. They pack in a suitcase for use in a rental car. You can program your destination and parameters into the portable at your leisure rather than only while in the car. "Consumer Reports" advises a screen size of 3.5-inches—that's big enough to see, along with a keypad big enough to use, and still be highly portable.

In-Car Mounting
Next, mounting. Unless you can guarantee you'll never have to come to a quick stop or swerve sharply to avoid an accident, forget the beanbag-mounted GPS that sits on top of your dash. A much more stable system is one that sticks to the windshield with a suction cup (unless you live in California or Minnesota where windshield-mounted anythings are against the law). The angled rigid arm is the best of the windshield mounts. The alternatives—ball-in-socket or gooseneck—may end up jiggling and bobbing.

Charge It
Most portable GPS systems include a rechargeable battery with a varying amount of life—some up to four hours. All can be plugged into your vehicle's 12-volt socket. The rechargeable systems are more versatile, especially if they include an AC power adapter.

Map Data
Early GPS units included limited map databases. If you wanted to expand that database, you had to download additional maps over the Internet, a process incompatible with spontaneity. Today's GPSs should include maps of the United States already installed.