Map projections — Geography, 14–17 years
A map projection is a chosen way to show the curved Earth on a flat surface, knowing that some property will change.
Turning a globe into a map
A globe shows Earth’s shape fairly naturally, but it is awkward to fold, print or carry. A map projection transfers the curved surface onto a flat page or screen. Because a curved surface cannot become flat without stretching, shrinking or tearing, every projection changes some distances, areas, shapes or directions.
Why no world map is perfect
People needed flat maps for travel, teaching, planning and comparing places. But choosing what to preserve creates a trade-off: a navigation map may keep directions useful, while an area map may keep countries’ relative sizes more faithful. The projection is therefore part of the map’s purpose, not a neutral window onto Earth.
Mercator’s scale at 60° north
In the Mercator projection, the scale factor is approximately 1 ÷ cos(latitude). At the Equator, cos 0° = 1, so the factor is 1. At 60° north, cos 60° = 0.5, so 1 ÷ 0.5 = 2. A region near 60° N is therefore shown at about twice the scale of one near the Equator, which makes it look larger.
A big shape is not always a big place
Many people see Greenland drawn larger than Africa and conclude that Greenland has more area. This is a reasonable mistake because the outline and visual size feel like direct measurements. On common Mercator maps, places near the poles are enlarged; Africa is actually about fourteen times larger than Greenland. Always check the projection before comparing areas.
Choosing the right map
Online maps often use a projection that keeps local directions and distances useful, even though the whole world is distorted. A map showing global population or forest loss should use a projection that compares areas fairly. Architects, sailors, scientists and data designers all choose projections according to the question they need the map to answer.
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