Who can see where you are when you tweet?

“There is all sorts of information that can be gleaned from things outside of the tweet itself,” says Chris Weidemann. (Credit: Steve Snodgrass/Flickr)

Location information from Twitter profiles is more publicly available than most people realize.

A new study published in the International Journal of Geoinformatics looks at the public geospatial data generated by Twitter users and how third parties could potentially use that information.

“I’m a pretty private person, and I wish others would be more cautious with the types of information they share,” says Chris Weidemann, a graduate student in University of Southern California’s Geographic Information Science and Technology (GIST) program.

‘Geospatial footprint’

Twitter has approximately 500 million active users, and reports have shown that 6 percent of users opt-in to allow the platform to broadcast their location using global positioning technology with each tweet they post.


That’s about 30 million people sending geo-tagged data out into the Twitterverse. In their tweets, people can choose whether their information is displayed as a city and state, an address, or they can pinpoint their precise latitude and longitude.

That’s only part of their geospatial footprint. Information contained in a post may reveal a user’s location. Depending upon how the account is set up, profiles may include details about their hometown, time zone, and language.

“There is all sorts of information that can be gleaned from things outside of the tweet itself,” says Weidemann, a geospatial technology manager for a Virginia company that builds geographic information systems for the federal government.

Finding trends

To get a fuller picture of what that collection of data might reveal about a Twitter user, Weidemann developed an application called Twitter2GIS to analyze the geospatial data generated by Twitter users.

Using Twitter’s API and Google’s Geocoding API, Twitter2GIS collects tweets from either a geographic region or a specific Twitter user. That geospatial information—or ambient data—is processed by Esri ArcGIS, a GIS software program used to map and analyze data, searching for trends.

During the sampling period, an average of 4 million Twitter users divulged their physical locations through global positioning system coordinates or other active location monitoring.

Additionally, 2.2 percent of tweets—about 4.4 million tweets a day—provided substantial ambient location data in the text of their posts.

Marketing or more?

By harvesting geospatial information, corporations could potentially build profiles of individuals for marketing purposes. However, it also opens users to more malicious intent.

“The downside is that mining this kind of information can also provide opportunities for criminal misuse of data,” Weidemann says.

An application similar to Twitter2GIS could also potentially be developed to mine data from other social media outlets.

For his master’s thesis, Weidemann is taking his application one step further and expanding it to allow Twitter users to login in with their profile credentials so they can view their own Twitter geospatial footprint. They can test out the beta version and provide feedback on the app at http://geosocialfootprint.com.

Weidemann will continue to add functionality to the app during the fall semester, such as its ability to analyze the content of tweets. “My intent is to educate social media users and inform the public about their privacy,” Weidemann says.

Source: USC