Great importance is attached to appearance of maps because the look of a map is a great factor of readability. In that sense, we also think that map users are confident of some recognizable styles, in particular in topographic map design. If we could formalize topographic styles, we should be able to propose to users automated methods to apply well-known styles on their data. This paper presents a part of a PhD thesis aiming at formalizing cartographic styles, especially what is meaningful according to related geographical spaces and cartographic practices. A method of comparison of topographic maps, based on French and Swiss topographic maps is detailed: our purpose is to distinguish which parameters and processes in the map design process make a significant visual impact, thus conveying a topographic style.