The lead author of the study, Chris Weidemann said that there are all sorts of information that can be gleaned from things outside of the tweet itself.
Weidemann developed an application called Twitter2GIS, to analyze the metadata collected by Twitter, including details about the user's hometown, time zone and language and found that roughly 20 percent of the tweets collected showed the user's location to an accuracy of street level or better.
The study revealed that many Twitter users divulged their physical location directly through active location monitoring or GPS coordinates but another 2.2 % of all tweets, equating to about 4.4 million tweets a day, provided so-called 'ambient' location data, where the user might not be aware that they are divulging their location.
Weidemann said that mining this kind of information can also provide opportunities for criminal misuse of data.
The study reveals important factual data for a growing national conversation about online privacy and third party commercial or government use of geo-tagged information and Weidemann said that the research had been fun and a little scary.