Online Maps That Steer You Wrong - New York Times
From an article in the NYT today:
As increasing numbers of travelers come to rely on the sites for directions (about four of five business trips are by car), they are discovering that computer maps can sometimes lead them astray.
Roughly 1 in 50 computer-generated directions is a dud, according to Doug Richardson, the executive director for the Association of American Geographers. He blames inaccurate road information for most of the failures.
'You have to have the latest data about road characteristics - things like one-way streets, turns and exits in your system in order for it to generate accurate directions,' he said.
Even if the streets remained static, online mapping would be an inexact science. Most of the major Web sites draw their data from a small group of competing suppliers and update their maps quarterly. They use a process called geocoding, which assigns a latitude-longitude coordinate to an address, to find a destination. Then their systems calculate the most efficient route. Each site handles the data in a slightly different way, which is why search results vary from mapping site to mapping site.