Location Extraction from Social Media: Geoparsing, Location Disambiguation and Geotagging

Location extraction, also called toponym extraction, is a field covering geoparsing, extracting spatial representations from location mentions in text, and geotagging, assigning spatial coordinates to content items. This paper evaluates five ‘best of class’ location extraction algorithms. We develop a geoparsing algorithm using an OpenStreetMap database, and a geotagging algorithm using a language model constructed from social media tags and multiple gazetteers. Third party work evaluated includes a DBpediabased entity recognition and disambiguation approach, a named entity recognition and Geonames gazetteer approach and a Google Geocoder API approach. We perform two quantitative benchmark evaluations, one geoparsing tweets and one geotagging Flickr posts, to compare all approaches. We also perform a qualitative evaluation recalling top N location mentions from tweets during major news events. The OpenStreetMap approach was best (F1 0.90+) for geoparsing English, and the language model approach was best (F1 0.66) for Turkish. The language model was best (F1@1km 0.49) for the geotagging evaluation. The map-database was best (R@20 0.60+) in the qualitative evaluation. We report on strengths, weaknesses and a detailed failure analysis for the approaches and suggest concrete areas for further research.