Mercator world map: real size of countries

Mercator projection: key facts and what it does to country sizes

Distortion class

Conformal

Graticule type

Cylindrical

Creator

Gerardus Mercator

Year

1569

Area

Highly distorted: enlargement grows toward the poles (Greenland looks larger than South America, though it is only about one eighth of its size)

Shape

Preserved locally (conformal projection)

Distances

Distorted: scale is true only along the equator (or chosen standard parallels) and grows toward the poles

Angles and directions

Preserved locally; every straight line on the map is a rhumb line, a line of constant compass bearing

Each of the thirty Tissot indicatrices on this map stays a circle. Mercator is conformal, so at every point it stretches the map equally along the meridian and along the parallel. Only the size of the circles changes, and it depends on latitude alone. The circles on the equator have their true diameter, the ones at 30° are 15% wider, and at 60° the diameter has doubled and the area has grown fourfold. Longitude plays no part: a circle over the Pacific and one over Africa in the same row look identical.

Poland makes an easy test, because its center lies near 52°N. There Mercator stretches every length 1.6 times and enlarges area 2.6 times compared with the equator. Drag its outline to the equator and it covers less than 40% of its current map area. Move it to 72°, roughly the latitude of central Greenland, and the linear scale rises to 3.2 and the area factor to about 10.5, so Poland looks about four times larger than in its real place. Its shape stays the same, because angles remain true.

The area isocoles run as straight horizontal lines: double area at 45°, four times at 60°, eight times at about 69.5° and sixteen times at 76°. The area-distortion heatmap therefore changes color in bands parallel to the equator. The angular isocoles stay empty, because no angle on this map is distorted. Turn on the equator, tropics and polar circles as well: the band from the tropic to the polar circle is 2.7 times taller on the map than the band from the equator to the tropic, although in degrees of latitude it is only 1.8 times wider.