Event-related image retrieval: exploring geographical and temporal distribution of user tags

Providing effective tools to retrieve event-related pictures within media-sharing applications, such as Flickr, is an important but challenging task. One interesting aspect is to search pictures related to a specific event with a given annotated image. Most existing methods have focused on doing this by extracting visual features from the pictures. However, pictures in media-sharing applications increasingly come with location information, such as geotags. Therefore, we stress the importance of exploring the possibility to leverage on the geographical and temporal distribution of terms in a tag-based search process, within event-related image retrieval. Specifically, we propose extended query expansion models that exploit the information about the temporal neighborhoods among pictures in a collection, and leverage on the geo-temporal distribution of the candidate expansion terms to reweight and expand the initial query. To evaluate our approach, we conduct extensive experiments on a dataset consisting of pictures from Flickr. The results from these experiments demonstrate the effectiveness of our method with respect to retrieval performance.