Determining the geographic focus of digital media is an essential first step for modern geographic information retrieval. However, publicly-visible location annotations are remarkably sparse in online data. In this work, we demonstrate a method which infers the geographic focus of an online document by examining the locations of Twitter users who share links to the document. We apply our geotagging technique to multiple datasets built from different content: manually-annotated news articles, GDELT, YouTube, Flickr, Twitter, and Tumblr.
@cite_0: Increasingly user-generated content is being utilised as a source of information, however each individual piece of content tends to contain low levels of information. In addition, such information tends to be informal and imperfect in nature; containing imprecise, subjective, ambiguous expressions. However the content does not have to be interpreted in isolation as it is linked, either explicitly or implicitly, to a network of interrelated content; it may be grouped or tagged with similar content, comments may be added by other users or it may be related to other content posted at the same time or by the same author or members of the author's social network. This paper generally examines how ambiguous concepts within user-generated content can be assigned a specific formal meaning by considering the expanding context of the information, i.e. other information contained within directly or indirectly related content, and specifically considers the issue of toponym resolution of locations.
The work in @cite_0 uses co-occurrences of toponyms in tags of geotagged Flickr photos, but expands the scope of closeness between toponyms to include tags made by the same user and by contacts within the user's social network. This assumes that links in a social network strongly correlate to users' location, in other words that closeness centrality in the social network is significant. This is not an assumption that we have seen in other toponym resolution publications, but it is a central thesis of our proposed methods. The results of @cite_0 show that toponym resolution is improved by including the posts of contacts, but that adding the posts of contacts of contacts does not perform as well.