Why Map Projections Matter in Human Geography

Every flat map of the Earth is a lie—a controlled, necessary lie. Because the planet is a sphere (more accurately, a geoid), representing its curved surface on a flat sheet of paper or screen always requires distortion. A map projection is the mathematical transformation that accomplishes this, converting latitudes and longitudes from the globe to planar coordinates. The choices mapmakers make in selecting a projection directly shape how we see the world, influencing everything from colonial boundaries to modern resource allocation. In human geography, these choices are particularly consequential because they affect how we visualize population distribution, perceive the relative importance of regions, and design policies based on spatial data.

Understanding map projections is not a niche technical concern; it is a fundamental literacy for interpreting demographic patterns, geopolitical arguments, and environmental data. As this article will show, different projections preserve different properties—area, shape, distance, direction—and each trade-off has implications for how we understand where people live, how densely they are concentrated, and which parts of the world appear dominant.

Historical Roots: From Navigation to Colonial Cartography

The most famous projection in history, the Mercator projection (1569), was designed for nautical navigation. Gerardus Mercator aimed to preserve angles and directions along rhumb lines, allowing sailors to plot straight-line courses. It achieved this by expanding distances as latitude increased, making Greenland appear larger than Africa and Antarctica stretch across the bottom like an endless white shield. For centuries, Mercator became the default world map in classrooms and atlases, embedding a Eurocentric worldview in generations of students. The distortions inflated Europe and North America, while shrinking Africa and South America, subtly reinforcing colonial-era power dynamics.

In the nineteenth and twentieth centuries, competing projections emerged, each with its own agenda. The Gall–Peters projection (first published in 1855, popularized in the 1970s) was explicitly political, aiming to correct the Mercator’s area distortions by presenting an equal-area representation. Critics claimed it made Africa and Latin America look “correctly large,” but shape distortion made continents appear stretched and unfamiliar. The debate between Mercator and Peters became a proxy war over representation, equity, and objectivity.

Key Properties Distorted by Projections

All flat maps distort at least one of four properties: area, shape, distance, or direction. No projection can preserve all simultaneously.

  • Conformal projections preserve local shape and angles but distort area (e.g., Mercator, Lambert Conformal Conic).
  • Equal-area projections preserve the correct relative sizes of regions but distort shape (e.g., Gall–Peters, Mollweide, Eckert IV).
  • Compromise projections balance distortions across properties, offering a visually pleasing middle ground (e.g., Robinson, Winkel Tripel, Adams World in a Square II).
  • Azimuthal projections preserve direction from a central point but distort area and shape elsewhere (e.g., Lambert Azimuthal Equal-Area for polar maps).

For human geography and population studies, the choice between conformal and equal-area is paramount. A conformal map may exaggerate the size of high-latitude countries, making their populations appear more spatially extensive than they are. An equal-area map corrects that visual bias but may render coastlines and shapes unrecognizable, potentially confusing students and decision-makers.

How Projections Shape Perceptions of Human Geography

Human geography examines the spatial organization of human activity—settlements, cultures, economies, and political systems. Map projections subtly encode assumptions about what matters. Consider two common examples:

The Mercator Effect: Overstating High-Latitude Regions

On a Mercator map, Greenland appears roughly the size of Africa. In reality, Africa is about 14 times larger. The same distortion makes Canada, Russia, and Scandinavia look immense, while equatorial countries like Indonesia and the Democratic Republic of the Congo shrink. A student seeing Mercator in a classroom might conclude that Europe and North America dominate the planet in land area, when in fact Africa can contain the entire contiguous United States, China, India, and western Europe combined. This perceptual bias has real-world consequences: it can influence how funding for development, disaster relief, or environmental conservation is allocated. A policymaker who subconsciously equates cartographic size with importance might prioritize regions that appear larger on a map.

Equal-Area Projections: Correcting the Balance

The Gall–Peters projection and its modern descendants, such as the Equal Earth projection (2018), aim to represent landmasses with accurate area ratios. When population distribution is overlaid on an equal-area map, the real concentrations become visually apparent. Africa, South Asia, and East Asia occupy vast swaths of the map, matching their demographic weight. This can challenge Eurocentric narratives and help students recognize that the highest population densities are in regions traditionally depicted as small under Mercator. However, equal-area projections often distort shapes, making continents look “stretched” along parallels. This can create a different kind of misperception—that population patterns are somehow less orderly or more elongated than they are on a globelike representation.

Population Distribution and the Choice of Projection

Demographic maps rely heavily on projection choice. A choropleth map showing population density by country or region will look drastically different depending on whether it uses a conformal or equal-area projection. For instance, a map using the Mercator projection will give more visual area to Canada and Russia, where population densities are low, while compressing India and Bangladesh, where densities are high. That visual weighting can mislead viewers into thinking densely populated regions are smaller and less spatially extensive than they actually are.

Dot Density Maps and Projections

Dot density maps place a dot for a set number of people (e.g., one dot per 10,000 inhabitants) within a geographical area. If the projection distorts area, the dots will be spread unevenly in the map space, potentially creating clusters where there are none or suggesting homogeneity where data is sparse. Equal-area projections are preferred for dot density maps because they maintain consistent geographic area for dot placement. Using a projection like the Mollweide or Aitoff ensures that a square centimeter on the map represents the same land area everywhere, allowing accurate visual comparison of population clusters across the globe.

Gridded Population Data and Modern GIS

Modern population datasets, such as WorldPop or the Gridded Population of the World (GPW), are stored in raster format on geographic coordinate systems. When displayed on a map in a GIS, the software reprojects the data on the fly. If the default projection is Web Mercator (used by most web mapping platforms), the raster cells near the poles are stretched vertically. This can cause population counts to appear concentrated in the middle latitudes, artificially reducing the visual impact of high-latitude settlements like Nuuk, Reykjavik, or Anchorage. Analysts must carefully review the projection associated with their basemap to avoid misinterpretation.

Modern Cartographic Practice: Web Mercator and Its Critics

The Web Mercator projection, a variant of the classic Mercator, has become the de facto standard for online maps, including Google Maps, OpenStreetMap, and Bing Maps. Its conformal property keeps local shapes and angles correct, which is useful for street-level navigation and zooming. But it inherits the area distortion of Mercator, making Greenland look as large as South America and Antarctica appear as a vast band across the bottom. For human geographic analysis of population distribution at a global scale, Web Mercator is a poor choice.

Fortunately, many web mapping libraries now allow users to toggle projections. The Equal Earth projection, designed by cartographers Bojan Šavrič, Tom Patterson, and Bernhard Jenny in 2018, offers an equal-area view with pleasing overall aesthetics, resembling the familiar Robinson projection but with correct areas. It is increasingly adopted for thematic mapping of population, climate, and environmental data. The AuthaGraph projection, developed by Japanese architect Hajime Narukawa in 1999, aims to preserve relative sizes and shapes with minimal distortion across the entire globe, even allowing the world to be tiled in seamless rectangles—an idea that challenges the rectangular grid of traditional maps.

Why Projection Choices Are Political

In human geography, maps are not neutral. They are authored artifacts that reflect the worldview of their creators. The Hobo–Dyer projection, published in 2002 by Robert Hamilton, is an equal-area cylindrical projection that places the equator slightly south of the map’s vertical center, thereby centering Africa and South America. Its creators explicitly intended to counter the northern bias of maps like Mercator. Although it distorts shapes, it has been adopted by organizations such as UNESCO and Oxfam for educational materials to promote a more equitable global perspective. The debate over which projection to use in textbooks and news media is ongoing, with some arguing that Mercator should be retired entirely from educational contexts.

Practical Implications for Policy and Research

The influence of map projections extends beyond education and into high-stakes decision-making. When planners evaluate the geographic distribution of a population for infrastructure projects, disaster response, or electoral districting, they must choose a projection that preserves the relevant metric. For example:

  • Equal-area projection should be used for calculating population density, resource coverage, or proportional representation.
  • Equidistant projection (preserving distances from a central point) is appropriate for measuring travel times or emergency response radii.
  • Conformal projection is best for local scale mapping, such as city street networks or property boundaries, where shape accuracy matters.

A failure to select the correct projection can lead to serious errors. In one infamous case, a 2008 flood risk map of Bangladesh used the Mercator projection, which significantly compressed the country’s area relative to its true size. The resulting map misrepresented the spatial extent of floodplains and led to underestimation of the population at risk. Such mistakes cost lives and money.

Future Directions: Interactive Maps and Multiple Projections

Advances in digital cartography are beginning to dissolve the tyranny of a single projection. Online interactive globes (e.g., CesiumJS, Earth Engine) allow users to view population data on a 3D globe, eliminating distortion altogether. But for print and 2D screen displays, projection remains necessary. New composite projections, such as the Adaptive Composite Map Projection, automatically select the best projection for the region being viewed, reducing distortion for localized analysis. The Equal Earth projection has become the default for global thematic maps in the popular QGIS software, and many journal guidelines now recommend authors specify the projection used in their figures.

For population distribution studies, we will likely see greater adoption of equal-area projections designed to minimize shape distortion in populated latitudes. The Winkel Tripel projection (used by the National Geographic Society since 1998) and the Robinson projection remain popular for reference maps because they offer a satisfying balance of shape and area. However, for any map that conveys quantitative data—population counts, density, migration flows—the safest choice is an equal-area projection combined with a clear scale bar and explanatory notes.

Conclusion: Seeing the World Accurately

Map projections are far more than technical curiosities; they are lenses through which we interpret human geography and population distribution. The Mercator projection, though historically useful for navigation, has perpetuated a distorted view of the world’s land area and, by extension, its people. Equal-area projections correct that distortion and reveal a more demographically accurate picture: a world where Africa, South Asia, and East Asia dominate in both land and population, where the global north appears less expansive, and where the true density patterns of humanity become visible.

Anyone who works with geographic data—geographers, urban planners, epidemiologists, journalists—must cultivate critical map literacy. That means asking: Which projection is being used? What does it preserve? How does it shape the viewer’s perception of the data? By making deliberate choices about projection, we can create maps that illuminate rather than mislead, enabling more equitable and informed understanding of our shared human geography.

Further reading: For a deeper dive into the politics of cartography, see “How Maps Work: Representation, Visualization, and Design” by Alan M. MacEachren; for an accessible history of map projections, consult “The Map Projection Revolution” by John P. Snyder; and for contemporary debates, read Scientific American’s coverage of the Equal Earth projection.