“I bought an expensive GPS navigator. Why is it always wrong?” New GPS owners are sometimes perplexed when their high-tech gadget gives them bad information, or can’t locate the street or business they are trying to find. In almost all cases the problem is not with the GPS, which is doing exactly what it’s supposed to do. More likely the problem is with the preloaded GPS maps, which can quickly become out of date.

GPS Update Required

GPS systems triangulate satellite signals to determine the receiver’s location with pinpoint accuracy. What many people don’t understand about GPS, however, is that the maps and various additional layers of information needed to make the positional signal useful come from a very different source. Forget satellites—information for every GPS update is collected on the ground, by people actually driving the road network and recording information. In other words, it's a much slower process.

An interesting article on gpsreview.net describes how GPS road and city maps are made, and why they are often out of date. Two main mapping companies provide the data for most major GPS navigators. They send drivers out to map new roads and newly developed areas, and re-map areas where customer feedback suggests the old maps are no longer accurate. (I wonder how today's high fuel prices are affecting the scope and frequency of these surveys.) The mapping companies update their GPS databases constantly, but it can take a long time for GPS manufacturers to convert all the latest information into their own software formats and produce GPS updates—usually in the form of a CD or DVD—for distribution.

The timing of GPS map updates for specific brands and models is often hard to predict. You may buy a new unit with pre-installed mapping software, only to see new software released soon after. This together with the cost of the mapping updates is a common source of irritation for GPS users. Mapping companies and GPS manufacturers often prioritize areas for updating based on customer feedback. But given the magnitude of the task, it can often take some time for complaints from customers regarding a particular area to be translated into a new DVD with all the corrections made.

Some companies are taking steps to speed the correction process. Last year TomTom introduced MapShare technology in their GO 720 GPS receiver. Rather than having to wait for mapping companies like NAVTEQ to schedule and carry out new surveys, MapShare allows TomTom users to provide feedback on route changes and mapping errors directly into a database accessible to other users—a kind of wiki approach to updating geographic information. TomTom users can choose whether or not they want to download customer-generated GPS updates, or only those verified by the manufacturer.

Other major GPS companies and car manufacturers issue update discs periodically. Of course when GPS users purchase these updates, there’s no guarantee that any deficiencies they may have noted in coverage of their own driving areas will have been corrected. Users of PDA-based GPS units have more options in the kinds of maps they can install. You can update Garmin iQue units, for examples, with data produced directly from mapping companies like NAVTEQ and Mapopolis. This approach makes a lot of sense—but unfortunately users of most portable and dashboard-mounted GPS navigators still have to wait for new GPS map updates from the manufacturer.