The development of numerous information sharing platforms have led to the emergence of multimedia user-generated content. With the prevalence of networking mobile devices and Global Positioning System (GPS) functionality, these contents could also be tagged with their location (geo-tagged) and visualised on a map through a geospatial information system. This in turn raises new challenges to manage the information retrieval process due to the potentially large amounts of data presented on the map. In this paper, we present a spatial clustering approach to enhance the searching feature of MobiTOP, a geospatial annotation system. The technique, which is a modification of DBSCAN (Density based spatial clustering applications with noise) coupled with our ranking schemes, is compared against other techniques. The evaluation results suggest the viability of our approach, and implications are also discussed.

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We investigate the usability of MobiTOP (Mobile Tagging of Objects and People), a mobile location-based annotation system. MobiTOP allows users to annotate real world locations with both multimedia and textual content and concurrently, share the annotations among its users. Equipped with a new interface as well as additional functionality such as clustering of annotations and advanced search and filtering options, a usability evaluation of MobiTOP was conducted in the context of a travel companion for tourists. The results suggested the potential of the system in terms of functionality for mobile content sharing. Participants agree that the features in MobiTOP are generally usable as a content sharing tool. Implications and future work are also reported in this paper.