The aim of the paper is to present the preliminary results obtained through a composite data processing system using multiple correspondence analysis in order to perform data fusion and deduce rules of spatial organisation. After describing a case study on the cartography of Ambrosia artemisiifolia (common ragweed), currently investigated on the Urban Community of Montreal (Canada) territory, the authors present an overview of the methods implemented for the digitalisation and interpolation of data and discuss methodological problems raised in the course of the study. Finally, avenues for future research conclude the paper.