Happy Valentine’s Day, from the District of Columbia

Map projections are fascinating areas of geographic study, we’re all intimately familiar with the Mercator projection, all of us having seen it for years in schools around the world. The primary problem is that the Mercator map was not designed for use as a political or physical map on the world. It was designed for navigation. Map projections are coerced compromise, the coercion comes when cartographers and geographers attempt to display the three dimensional form of our planet onto a two dimensional surface (like a computer screen or piece of paper). The compromise is in one of several areas: area, shape, direction, bearing, distance, and scale. It is impossible to preserve each of these components, although very large scale maps (meaning maps of very small areas) come the closest to reality. Maps of the entire world, on the other hand, have significant compromises. In Mercator’s map, direction and bearing is maximized so you could pick a heading in your boat from New York, follow it on Mercator’s map, and know exactly where in Europe you would land. As a political map, its horrible. Area, shape, and scale are horribly distorted. Greenland looks big enough to be its own continent, as a kid I think I even asked my teacher why Australia was one but Greenland wasn’t.

Other maps make compromises between all of map’s components, distorting each one. While not totally accurate in any one area, they aren’t completely inaccurate either.

While the Bonne projection could have been made for Valentine’s Day, it was probably not meant to depict the entire world. The wikipedia page for Rigobert Bonne (1727-1795) notes that he worked as Royal Hydrographer in France. His occupation suggests that the projection was meant for depictions of coastal areas, indeed the projection itself preserves scale along latitude (which are concentric circles). In addition, shape is not distorted along the central meridian and the standard latitude, that is the north-south and east-west line on which the projection rests. These properties would make the projection effective for depicting coastlines where distance and shape are important to map accuracy. Bonne was not the original developer of this projection, as the wikipedia article explains.

the Sylvano, Honter, de I'Isle, Coronelli, Bonne, Bonne projection

the Sylvano, Honter, de I’Isle, Coronelli, Bonne, Bonne projection

I would have suggested that Sylvano’s map from 1511 was made in the (modern) spirit of Valentine’s Day, but I don’t think cannibalism is a part of the modern Valentine tradition. Don’t believe me? Go take a look, just above the equator in what would be “the New World.”


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