An important part during preparatory work of map production is the structuring of the thematic content and as such also in the creation of the legend. After looking into the subject of the map in detail, the cartographer has to decide how the single thematic elements should be grouped, arranged and named.

Prior to map construction, he also has to have a clear vision of the layout of the map. Content, structure and placement of titles, and marginal data as well as of the legend have to be determined. To visualise these ideas, it is recommended to draft a map sketch manually.