On the Relative Importance of Toponyms in GeoCLEF

In this work we attempted to determine the relative importance of the geographical and WordNet-extracted terms with respect to the remainder of the query. In our system, geographical terms are expanded with WordNet holonyms and synonyms and indexed separately. We checked the relative importance of the terms by multiplying their weight by 0.75, 0.5 and 0.25. The comparison to the baseline system, which uses only Lucene, shows that in some cases it is possible to improve the mean average precision by balancing the relative importance of geographical terms with respect to the content words in the query. We also observed that WordNet holonyms may help in improving the recall but WordNet has a small coverage and term expansion is sensible to ambiguous place names.