2.1. Introduction

Whether it be from the point of view of the biologist who works on a scale from particle to organism, or from that of social sciences and particularly the geographer analyzing events on a scale from individual to territory, notions of scale and scale changes are at the core of many discussions: we strive to understand relations or interactions between entities relative to different scales. The analysis or the modeling of these interactions has become a necessity for any discipline.

In geography, the notion of scale can be a source of ambiguity. It is always used in the sense of spatial resolution, but it can just as well refer to cartographic representation or levels of observation and analysis ^[1]. Here, we are focusing on the latter. Today, we no longer have to demonstrate that the analysis of a spatial event is directly linked to the geographical level of observation representing granularity, i.e. the order of magnitude chosen for the analysis. This leads to the consideration of space in relation to different orders of magnitude, each defining distinct perception levels.

With the development of geographic information systems (GIS), the acquisition of knowledge at different scales and the transition from one level to another are becoming technically easier. However, this creates new conceptual and methodological problems. Processing and management of data at different geographical scales will now become multidisciplinary, involving computer scientists, statisticians, geographers and other scientists...