A thematic map is a map that illustrates more than simply geographical relationships or locations, but rather also portrays themes, patterns, or data relating to physical, social, medical, economic, political, or any other aspect of a region or location. Examples include maps that show variations of population density, climate data, wealth, voting intentions, or life expectancy with geographical location. These tools have become central to the work of scientists, practitioners, and students in nearly every field, from epidemiology to political science, and are familiar to members of the public as a common means of expressing complicated and multivariate information in easily understood graphical formats. This set of three volumes on Thematic Cartography considers maps as information constructs resulting from a number of successive information transformations and the products of decision stages, integrated into a logical reasoning and the order of those choices. It thereby provides a thorough understanding of the theoretical basis for thematic mapping, as well as the means of applying the various techniques and methodologies in order to create a desired analytical presentation. This first volume introduces the basics of thematic cartography. The authors present the transformations necessary to the production – using a scientific approach – of any thematic map. Four stages are detailed: from geographic entities to cartographic objects; the [XY] transformation; the [XYZ] cartographic transformations; and the semiotic transformation. Technical aspects giving map-reading keys are also included.