On many familiar world maps, Greenland looks almost as large as Africa. In reality, Africa’s area is roughly 14 times Greenland’s. The difference is not a mistake in the map: it is a consequence of the projection used to flatten a round Earth onto a rectangle.
The Mercator projection, introduced by Flemish cartographer Gerardus Mercator in 1569, was designed with navigation in mind. It remains useful for some purposes, but its expanding shapes and areas make it a poor choice for comparing the size of countries or continents. Knowing what it preserves—and what it distorts—helps explain why different maps can show the same world so differently.
A map that helps plot a compass course
Earth is curved; a flat map is not. Any map that represents the whole globe on a sheet or screen must make trade-offs. A projection can preserve some properties, such as local angles, while distorting others, including area, distance, or direction over long stretches.
Mercator’s projection preserves local angles and shapes. That feature is called conformality. It also gives a navigator a particularly practical visual shortcut: a route that maintains a constant compass bearing, called a rhumb line, appears as a straight line on the map. A sailor could draw that line and use it to set a steady course.
That straight line is not necessarily the shortest route between two points. On a globe, the shortest path between distant locations follows a great circle. On a Mercator chart, a great-circle route generally curves. The projection’s strength is making a constant-bearing course easy to plot, not showing every kind of route in its shortest form.
Why Greenland grows while the equator stays familiar
Mercator maps stretch land and sea more as they approach the poles. In the standard projection, the scale factor increases with latitude: it is about twice as large at 60 degrees north or south as it is at the equator. Because the stretching happens in both map dimensions, the apparent area grows even faster.
This is why Greenland, which lies mostly at high northern latitudes, appears enormous on a typical Mercator world map. Africa lies largely closer to the equator, where the projection’s scale is less inflated. The contrast is not evidence that one continent has been drawn incorrectly; it reflects the projection’s mathematical rules.
The distortion becomes extreme near the poles. In the standard Mercator projection, the poles cannot be shown as finite points: the map stretches without limit as latitude approaches 90 degrees. World maps using this projection therefore cut off the far north and south rather than displaying the poles.
Useful for one task, misleading for another
A projection is not simply “accurate” or “inaccurate” in every respect. Mercator’s shape and angle properties can be useful for navigation, but they make the projection unsuitable when the visual comparison of land area is the goal. A map that preserves area can make that comparison more honest, though it will distort shapes or directions in other ways.
That distinction matters when reading maps used in classrooms, news stories, or online. If a map is intended to show where places are, or to support a particular navigation task, its design may be appropriate. If it invites readers to compare the size of countries, the projection should be considered before drawing conclusions from the picture.
Some digital maps use a Mercator-derived projection because it is convenient for displaying and zooming into local areas. At high latitudes, though, the same visual enlargement remains. A projection that works well for streets or local navigation is not automatically a good choice for a world map meant to compare continents.
How to read a world map more carefully
- Ask what the map is for. Navigation, area comparison, and showing the whole globe call for different compromises.
- Look for the projection. A map’s legend, caption, or technical notes may name it. If no projection is identified, avoid treating the apparent sizes as precise comparisons.
- Check high-latitude regions. On Mercator maps, places near the poles are enlarged relative to places nearer the equator.
- Use an area-preserving map for area questions. It will still have trade-offs, but it is designed to represent relative areas more faithfully.
The Mercator projection has endured because it solves a real problem: it turns a constant compass course into a straight line that can be plotted on a flat chart. Its familiar world view also carries a visual cost. Greenland’s outsized appearance is a reminder that every flat map is a particular way of translating a curved world—not a neutral window onto it.
