If cartography is a form of communication, the measure of a good map is how well it conveys information to its readers to enlighten, convince, or persuade. Too often the pure aesthetic appeal of a map is equated with its communicational value. Aesthetic issues certainly play a role in effective cartography, but it is the issue of communication that holds the central role in cartographic design. This means that one always begins a project by considering the message to be conveyed and the audience to be addressed. In effect, the question asks what the reader should gain from the map or how the reader should respond.
Motives vary greatly.
Many maps are intended solely to convey accurate information about spatial relationships, others to sway public debate. A cartographer must be able to identify the type of reader being addressed for two principal reasons. First, it is important to have an idea about what the audience is likely to know about the subject matter of the map. Second, it is useful to know how much background the readers have in using maps. A map intended for specialists who have a background in cartography might be organized far differently than one intended for use as a prop in a public debate.