Cheshire II at GeoCLEF: Fusion and Query Expansion for GIR

In this paper I will describe the Berkeley (group 1) approach to the GeoCLEF task for CLEF 2005. The main technique we are testing is the fusion of multiple probabilistic searches against different XML components using both Logistic Regression (LR) algorithms and a version of the Okapi BM-25 algorithm. We also combine multiple translations of queries in cross-language searching. Since this is the first time that the Cheshire system has been used for CLEF this approach can, at best, be considered a very preliminary base testing of some retrieval algorithms and approaches. The primary geographically based approaches taken for GeoCLEF were to georeference proper nouns in the text using a gazetteer derived from the World Gazetteer with both English and German names for each place, and to expand place names for regions or countries in the queries by the names of the countries or cities in those regions or countries.