One place, several useful maps

Two maps of the same place can look quite different while both serving their intended readers well. A transport map may simplify the shapes of routes to make connections easy to follow. A walking map may preserve street geometry more closely because distance and direction matter to someone moving between buildings.

[A] Selection is unavoidable when a large area is represented on a small page. [B] Minor features may disappear, symbols may replace detailed shapes, and crowded labels may need to be repositioned. [C] These changes can improve readability, but they must not obscure relationships essential to the map's purpose. [D]

A reader therefore needs to know what kind of question the map can answer. A diagram that clearly shows where to change trains may be a poor guide to the shortest walk between stations. Treating it as a precise street plan would confuse a deliberate simplification with an error.

Map evaluation should consider both accuracy and use. The relevant test is whether the representation preserves the information its audience needs, while making its conventions understandable. A map is neither a complete copy of a place nor a freely invented picture. Its choices should support a clearly defined task.