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The growth of various web 2.0 applications (e.g. forum, interactive mapping platforms, and social media) provides a new approach to create and disseminate user-generated geographic content over the Internet. Such content is termed as Volunteered Geographic Information in the domain of Geographic Information Science (VGI, Goodchild, 2007). In this research, we focused on a subtype of VGI, text-based VGI, which consists of short texts with geographic attributes.
Text-based VGI recently played a critical role in disaster management. It has the potential to provide crucial information and enhance situational awareness, particularly in chaotic situations of response of extreme events. For example, in several extreme events such as the 2010 Haiti Earthquake and the 2011 Queensland Floods, an emergency reporting platform “Ushahidi” was used by the volunteers to gather disaster information. Affected residents can report the presence and extent of incidents; the volunteers can aggregate information from multiple sources on the platform (McDougall, 2012; Potts, Lo, & McGuinness, 2011; Zook, Graham, Shelton, & Gorman, 2010). Ubiquitous social media is another important source of text-based VGI. Emergency Management (EM) stakeholders have used the social media stream in the communication, early identification of incidents, and emergency planning (Arklay, 2012; Shih, Han, & Carroll, 2015). These cases reflect that information access in mass emergencies has shifted to non-conventional models on the Internet. The use of VGI enhances the understanding of what is happening in existing conditions and how it could change over time.
Although text-based VGI can contribute significantly to disaster management, there is a major challenge in its use. In the context of extreme events, a huge number of VGI instances are available from relevant web applications. Some may provide informative content. Others may relate to an event but not provide any value to EM stakeholders. The text content quality of each information instance is hard to be assessed efficiently by manual efforts. In the literature, an automatic method for VGI text content quality assessment is to use the supervised learning model (e.g. Imran, Elbassuoni, Castillo, Diaz, & Meier, 2013; Imran, Mitra, & Srivastava, 2016). The supervised learning model can classify data to generate quality indicators. Currently, most previous work has sought a standard text classification approach which used only text-related features such as n-grams in the learning model. In this research, we propose an assumption that the geographic attributes of VGI (i.e. geographic features) can be used for modelling and can enhance the performance of learning models. According to Tobler’s first law of geography, “everything is related to everything else, but near things are more related than distant things (Tobler, 1970).” We assume that if a VGI instance is close to the flood-affected areas or has an informative neighbour spatially nearby, it is more likely to provide informative content as well. This geographic assumption has been discussed in a few case studies (e.g. Albuquerque, Herfort, Brenning, & Zipf, 2015; Craglia, Ostermann, & Spinsanti, 2012) but not yet evaluated in a small-scale study area (e.g. within a city) and via a supervised learning approach. Therefore, our research question is: within a small-scale study area, can geographic features be used for the development of a supervised learning model, and provide better performances than models without geographic features?
To evaluate our assumption, we propose an integrated method for VGI text content quality assessment. This integrated method combines text-related features and geographic features to train a supervised learning model. We tested the performance of this method in a case study using data collected from two previous flooding events in Brisbane, Australia. The remainder of this paper is structured as follows. Section 2 provides a literature review about the development of text-based VGI quality assessment methods. In Section 3, we present the research objectives and methodology. Section 4 describes the case study including the models and evaluations. Section 5 discusses the findings and limitations of our experiment and concludes this article.