1. A method for determining core geographical information in a document, the method comprising: identifying appearances of a plurality of geographical names in the document; determining one or more frequencies of each geographical name's appearances in the document; assigning one or more positional weights to each geographical name according to positions of the geographical name's appearances in the document; computing a score of each geographical name based on the one or more frequencies and the one or more positional weights of the respective geographical name; and determining the core geographical information in the document based on the scores of the plurality of geographical names.