1. A method of filtering geographical data, comprising: selecting a map region to be retrieved; receiving a retrieval object and a retrieval condition; outputting a trapezoidal interface; verifying a threshold corresponding to a height of the trapezoidal interface for each position of the map region; filtering the retrieval object satisfying the threshold or more or less in each position of the map region to extract the filtered object; and displaying the filtered object on the map region to output the displayed object.