Area fidelity (equivalence) is a term from card design theory . A map network design is said to be equivalent if it shows the size of an area (e.g. a country or continent) reduced by a certain scale and this scale is the same over the entire map. This is often only possible with strong distortions, especially at the edge of the map. Thus, an equal-area map is never triangular .
- Markus-Hermann Schertenleib, Helena Egli-Broz: Basics of geography: tasks of the subject, earth as celestial body and cartography Compendio Bildungsmedien, Zurich 2008, ISBN 978-3-7155-9368-5 .