In this paper we describe content determination issues involved in the Atlas.txt project, which aims to automatically describe georeferenced information such as census data as text for the visually-impaired (VI). Texts communicating geo-referenced census information contain census data abstractions and their corresponding geographic references. Because visually impaired users find interpreting geographic references hard, we hypothesized that an introduction message about the underlying geography should help the users to interpret the geographic references easily. We performed user studies to design and evaluate the introduction message. An initial evaluation study with several sighted users and one partially sighted user showed that an introduction message is certainly preferred by most participants. Many of them used an introduction message themselves when they described maps textually. But the study also showed that the introduction message made no difference when the participants were asked to draw maps using the information in the textual descriptions.