The process of reading a topographic map requires users to recognize and learn the cartographic symbols of the key (or legend) while interpreting the territory as depicted on the map at a given level of abstraction (the form and nature of features, their saliency and relationships). We present the results of an empirical user study that aims to identify and assess the main graphical characteristics that are used by map users to recognize the design principles which constitute the topographic mapping style adopted by IGN (Institut National de l'Information Géographique et Forestière), France. Our results suggest that 91% of the participants were able to recognize an IGN-France topographic map amongst other topographic map products. We also determine which graphical characteristics play a role in the recognition of this cartographic style, either by visual memory or by visual perception, and identify the representation of relief, including contour lines and shaded relief, as one of the major graphical characteristics of the topographic mapping style of IGN-France. Moreover, the participants of our study considered the representation of touristic POI (points of interest), toponymy, typography, the main roads network, the individual buildings and the forests, to be essential for stylistic recognition.

Keywords: geovisualization, cartographic continuum, topographic style, interpolation, map design, perception and cognition Geoportals and geovisualization tools provide to users various cartographic abstractions that describe differently a geographical space. Our purpose is to be able to design cartographic continuums, i.e. a set of in-between maps allowing users to navigate between two topographic styles. This paper addresses the problem of the interpolation between two topographic abstractions with different styles. We detail our approach in two steps. Firstly, we setup a comparison in order to identify which structural elements of a cartographic abstraction should be interpolated. Secondly, we propose an approach based on two design methods for maps interpolation.