SNAF: Observation filtering and location inference for event monitoring on twitter

Twitter has recently emerged as a popular microblogging service that has 284 million monthly active users around the world. A part of the 500 million tweets posted on Twitter everyday are personal observations of immediate environment. If provided with time and location information, these observations can be seen as sensory readings for monitoring and localizing objects and events of interests. Location information on Twitter, however, is scarce, with less than 1% of tweets have associated GPS coordinates. Current researches on Twitter location inference mostly focus on city-level or coarser inference, and cannot provide accurate results for fine-grained locations. We propose an event monitoring system for Twitter that emphasizes local events, called SNAF (Sense and Focus). The system filters personal observations posted on Twitter and infers location of each report. Our extensive experiments with real Twitter data show that, the proposed observation filtering approach can have about 22% improvement over existing filtering techniques, and our location inference approach can increase the location accuracy by up to 36% within the 3km error range. By aggregating the observation reports with location information, our prototype event monitoring system can detect real world events, in many case earlier than news reports.