Consumer Reports bases the overall score for each GPS unit it reviews on several categories, including ease of use, routing options, driving guidance, display quality and traffic interface, as of 2015. It also factors in screen size and, for mounted units, the mount design. The company recommends drivers base the GPS unit they choose on their lifestyles and desired features.
Lifestyle considerations for drivers to consider when purchasing a GPS unit, according to Consumer Reports, include typical driving conditions and how much time each driver spends in unfamiliar areas. Drivers who frequently encounter traffic should look for GPS units that provide traffic updates and plan routes with traffic conditions in mind.
Consumer Reports recommends checking for a built-in GPS systems when purchasing a new car, as those types of systems tend to be integrated well with the car's design. However, drivers who use multiple cars or travel frequently may prefer a portable GPS unit that isn't tied to a specific car.
Ease of use measures the simplicity of getting directions and adjusting the settings of the GPS unit. Routing options focuses on what type of features a unit offers for modifying a route. Driving guidance measures the clarity of the directions a unit provides. Display quality rates the screen of the unit. Traffic interface is the unit's ability to integrate traffic information.