Juan de la Cosa’s Projection: A Fresh Analysis of the Earliest Preserved Map of the Americas
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Previous cartographic studies of the 1500 map by Juan de La Cosa have found substantial and difficult-to-explain errors in latitude, especially for the Antilles and the Caribbean coast. In this study, a mathematical methodology is applied to identify the underlying cartographic projection of the Atlantic region of the map, and to evaluate its latitudinal and longitudinal accuracy. The results obtained show that La Cosa’s latitudes are in fact reasonably accurate between the English Channel and the Congo River for the Old World, and also between Cuba and the Amazon River for the New World. Other important findings are that scale is mathematically consistent across the whole Atlantic basin, and that the line labeled 'cancro' on the map does not represent the Tropic of Cancer, as usually assumed, but the ecliptic. The underlying projection found for La Cosa’s map has a simple geometric interpretation and is relatively easy to compute, but has not been described in detail until now. It may have emerged involuntarily as a consequence of the mapmaking methods used by the map’s author, but the historical context of the chart suggests that it was probably the result of a deliberate choice by the cartographer.
Juan de la Cosa
Tropic of Cancer
Robles Macias, Luis A. (2010). Juan de la Cosa’s Projection: A Fresh Analysis of the Earliest Preserved Map of the Americas. ALA Map and Geography Round Table. Available electronically from