new tracking system can pin internet users location with a few hundred meters

Unless you explicitly give permission to use your location, 

interested parties (like, say, advertisers) can only track you with geolocation to within a radius of about 200 kilometers. 

But researchers in China and the U.S. have figured out a way to get closer--much closer. 

With a three-stage system using Google Maps, these researchers can, according to New Scientist, 

get as close as a few hundred meters.