A longstanding problem with online maps and navigation devices is that your destination is often not where they say it is. When you reach the “destination”, you’re often a few hundred feet from where you wanted to be. There are three common reasons for this:

• No one has walked every street and identified where each address is. Addresses are approximated based on standard numbering schemes. On a block that goes from 200 to 300, 250 will be placed in the middle.
• Businesses sometimes use vanity addresses. The business may have an address on Madison Avenue in New York, but the real entrance is off less glamorous 54th Street.
• The business address is incorrect or malformed in the database.

Google Maps is now tapping users to help fix this problem. Users can edit the location markers for a given address. To prevent abuse, any movements greater than about 600 feet are moderated.

This is especially helpful for addresses that are incorrect in the Google database or can’t be accurately geocoded. These appear on Google Maps with a circle to mark the location and a warning.

The Pentagon Post Office is listed with an address of “The Penagon, Arlington, VA 22201”. As a result, it appears about three miles from where it really is. I was able to move it to the correct spot, on top of the Pentagon. Because this is more than 600 feet, the change will be moderated. I’ll be watching to see how quickly that happens. (Update: Google has since removed the Pentagon Post Office record altogether.)

If this feature takes off, it will make Google’s Street View feature much more useful. Right now, when you pull up a Street View of an address, there’s a good chance you won’t see the business you were looking for because it shows a view of the approximated location.

More on: Google, maps, satellite navigation