Understanding Map Projections: Why Every Map Lies (and How to Choose the Right One)
Every map you have ever looked at is wrong. Not because cartographers are careless, or because the data is inaccurate, but because of a fundamental geometric truth: you cannot flatten a sphere without distorting it. This is not a failure of mapmaking. It is a mathematical certainty, and understanding it changes the way you read every map for the rest of your life.
The Core Problem: Flattening a Sphere
Imagine peeling an orange. No matter how carefully you remove the skin in one piece, you cannot press it flat without tearing, stretching, or compressing parts of it. The Earth’s surface presents exactly the same challenge. It is a closed, curved surface — a shape mathematicians call a “non-developable surface” — and no amount of ingenuity can transfer it onto a flat plane without some form of distortion.
Cartographers call this distortion, and every map projection is essentially a different strategy for managing it. The key insight is that distortion cannot be eliminated — it can only be moved around and traded off. A map that preserves shape will sacrifice area. A map that preserves area will sacrifice shape. A map that preserves distance in one direction will distort it in another.
This is not a minor technical quibble. The choice of projection shapes how people perceive continents, countries, and the relationships between them. It carries real political, educational, and psychological weight.
The Four Properties Every Projection Must Compromise
Before diving into specific projections, it helps to understand the four spatial properties that cartographers try to preserve:
Conformality (Shape): A conformal projection preserves the local shape of small areas. Coastlines, borders, and landmasses look “right” at any given point, even if their overall size is distorted. Conformality requires that angles be preserved — the technical term is that the projection is “angle-preserving” or “orthomorphic.”
Equal Area (Area): An equal-area projection ensures that regions are shown in correct proportion to one another. If Russia is 170 times larger than Germany in reality, it will appear 170 times larger on the map. This comes at the cost of shape — landmasses near the edges of the map often appear stretched or squashed.
Equidistance (Distance): No projection can preserve all distances simultaneously, but some preserve distances along specific lines — usually from a central point or along certain parallels. These are useful for navigation and for measuring distances from a fixed origin.
Azimuthality (Direction): Some projections preserve the true bearing (compass direction) from a central point to all other points. This is particularly useful for aviation and long-range navigation.
The fundamental theorem of cartography, sometimes called Tissot’s theorem, formalizes what every mapmaker already knows intuitively: no projection can be both conformal and equal-area at the same time. Every map is, by necessity, a compromise.
A Brief Taxonomy of Projections
There are hundreds of named projections, but most fall into a handful of conceptual families based on the geometric surface used to mediate between the globe and the flat map.
Cylindrical Projections
In a cylindrical projection, the globe is conceptually wrapped inside a cylinder, which is then unrolled. The most famous example is the Mercator projection, created by Flemish cartographer Gerardus Mercator in 1569.
Mercator designed his projection specifically for navigation. Its defining property is conformality: at every point on the map, angles are preserved. This means that a straight line drawn on a Mercator map represents a constant compass bearing — a “rhumb line” — which made it invaluable for sailors plotting courses with a compass.
The cost is severe distortion of area at high latitudes. Greenland appears roughly the same size as Africa on a Mercator map. In reality, Africa is about 14 times larger. Antarctica, spread across the bottom of the map, looks like a continent-sized ice sheet stretching to infinity. The projection’s near-ubiquitous use in classrooms and wall maps throughout the twentieth century gave generations of people a profoundly skewed sense of the relative sizes of countries.
The Peters projection (more formally, the Gall-Peters projection) emerged in the 1970s as a direct challenge to Mercator’s dominance. It is an equal-area projection, meaning it shows all countries in their correct relative size. Africa and South America balloon outward; Europe and North America shrink. The map was embraced by development organizations and critics of Eurocentrism, and attacked by cartographers who pointed out that, in preserving area, it grotesquely distorted shape. Continents are stretched vertically near the equator and compressed horizontally near the poles. It trades one lie for another.
Conic Projections
Conic projections wrap the globe in a cone rather than a cylinder. They work best for mid-latitude regions with greater east-west than north-south extent, which makes them popular for mapping countries like the United States, Russia, and China.
The Albers Equal-Area Conic projection is standard for many U.S. government maps. It preserves area while keeping shape distortion reasonably low within the continental United States. The Lambert Conformal Conic is conformal rather than equal-area and is widely used in aeronautical charts and weather maps across mid-latitudes.
Azimuthal Projections
Azimuthal projections project the globe onto a flat plane that touches the sphere at a single point. All directions from that central point to any other point on the map are correct. They are often used for polar maps, where the plane is tangent to the North or South Pole.
The Azimuthal Equidistant projection is famous as the emblem of the United Nations. All distances from the center (the North Pole, in the UN’s case) are correctly scaled, making it an intuitive representation of the world from a single vantage point.
The Stereographic projection is conformal and has been used historically for navigational charts. The Gnomonic projection has the unusual property that all great circles — the shortest paths between two points on a globe — appear as straight lines, making it useful for planning long-distance flight routes.
Pseudocylindrical and Compromise Projections
A number of projections do not fit neatly into the above categories. They sacrifice both conformality and equal-area in exchange for a more visually balanced appearance.
The Robinson projection, designed by Arthur Robinson in 1963 at the request of Rand McNally, became widely used in atlases and textbooks from the 1980s onward. It is neither conformal nor equal-area, but it was designed to “look right” — to present a world that feels intuitively proportionate even though it is technically accurate in neither shape nor area.
The Winkel Tripel projection (the name means “triple compromise” in German, referring to its minimization of three types of distortion) was adopted by the National Geographic Society in 1998 for its world maps. It is widely considered one of the best general-purpose world map projections available, offering a clean, readable image with relatively low distortion across most of the globe.
The Goode’s Homolosine projection takes a different approach entirely: it interrupts the map, introducing deliberate cuts in the oceans (or, in some versions, the continents) to reduce distortion in the areas of greatest interest. The result looks like a peeled orange pressed flat — which is essentially what it is. It is excellent for showing the true shapes and sizes of landmasses, but the interruptions make it disorienting for showing relationships across oceans.
Why the Mercator Map Became the Default (and Why That Matters)
It is worth pausing to ask why the Mercator projection dominated popular cartography for so long when its distortions are so significant. Several factors converged.
First, Mercator’s navigational utility was genuinely revolutionary. For centuries, it was the most practically important map projection in existence, and its dominance in maritime charts gave it enormous cultural currency.
Second, it is a visually clean, aesthetically satisfying map. The rectangular grid, with horizontal lines of latitude and vertical lines of longitude, is orderly and easy to print and read. It fills a rectangular sheet of paper neatly.
Third, and more subtly, the projection’s distortions happened to flatter the nations that were producing and distributing maps. Europe appears larger than it is. The equatorial regions — home to Africa, South America, and much of Asia — appear smaller. This alignment between distortion and imperial geography was not coincidental to the projection’s persistence, even if it was not the explicit intention of its creator.
The broader lesson is that maps are never neutral. Every projection encodes assumptions about what matters, what should be centered, and what can be sacrificed. Reading a map critically means asking not just “what does this show?” but “what has been distorted to show it this way?”
How to Choose the Right Projection
The right projection depends entirely on what you are trying to communicate and where you are mapping. Here is a practical framework:
For world maps in general use: The Winkel Tripel or Robinson projection offers the best balance of shape and area accuracy. Avoid Mercator for any purpose other than navigation or tiled web maps.
For showing statistical data by region (choropleth maps): Use an equal-area projection. If regions appear larger than they are, they will draw more visual weight than they deserve. Albers Equal-Area Conic is excellent for the contiguous United States; Goode’s Homolosine or Mollweide works well for world maps.
For navigation and direction: Mercator remains the standard for maritime charts and is the basis for most web mapping tile systems (Google Maps, OpenStreetMap) because straight lines at constant zoom levels are easy to compute. Gnomonic projections are useful for planning great-circle routes.
For polar regions: Azimuthal projections centered on the poles work well. The Stereographic is conformal; the Lambert Azimuthal Equal-Area preserves area.
For continental or national maps: Conic projections generally work best for mid-latitude regions with greater east-west than north-south extent. For regions near the equator, cylindrical projections may be more appropriate.
For dramatic visual effect or thematic storytelling: Interrupted projections or unconventional orientations can break readers out of habitual assumptions. Flipping the map upside-down (south-up orientation) immediately defamiliarizes the viewer’s assumptions about which direction is “up” and why.
Tissot’s Indicatrix: Seeing Distortion Directly
One of the most useful tools for understanding any map projection is Tissot’s indicatrix, developed by French mathematician Nicolas Auguste Tissot in the nineteenth century. The idea is simple: place identical small circles at regular intervals across the globe, then project them onto the map. Where the circles remain circular, the projection is locally conformal. Where they become ellipses, shape is being distorted. Where the ellipses are all the same size, the projection is equal-area. Where they vary in size, area is being distorted.
Looking at a Tissot indicatrix for the Mercator projection makes the distortion viscerally obvious: near the equator, the circles are small and round. Near the poles, they balloon into enormous circles, showing just how drastically areas are inflated. For the Goode’s Homolosine, the circles remain similar in size (equal-area) but become increasingly elliptical toward the edges of each lobe (shape distortion).
If you are ever unsure about a projection’s properties, finding its indicatrix is the fastest way to understand what it preserves and what it sacrifices.
The Web Mapping Revolution and Its Distortions
The rise of digital mapping introduced a new default projection to billions of people: Web Mercator, also known as EPSG:3857. Used by Google Maps, Apple Maps, OpenStreetMap, and virtually every tile-based web mapping platform, it is a simplified variant of the Mercator projection optimized for fast computation in a square tile system.
Web Mercator inherits all of Mercator’s area distortions. Greenland still looks enormous. Antarctica still sprawls impossibly. But for the primary use case of these platforms — navigating cities, finding addresses, measuring driving routes — it works well. At street level, the distortions are imperceptible, and the conformal property means that local shapes are accurate enough for practical navigation.
The danger arises when web maps are used for anything beyond local navigation — for comparing country sizes, understanding geopolitical relationships, or forming impressions of the world at large. For those purposes, the platform’s default projection is actively misleading.
Conclusion: Every Map Is an Argument
The title of this article claims that every map lies. That is slightly unfair. A better framing is that every map makes choices, and those choices reflect values, priorities, and trade-offs. The mapmaker who chooses Mercator is not lying — but they are implicitly saying that navigational fidelity and visual neatness matter more than proportional representation. The mapmaker who chooses Peters is not lying — but they are saying that political equity in representation matters more than accurate shape.
Understanding projections does not mean distrusting maps. It means reading them as the arguments they are. It means asking what the maker chose to preserve, what they sacrificed, and why. It means noticing when the choice of projection shapes the message as much as the data does.
The world is round. Maps are flat. Everything in between is a negotiation — and the terms of that negotiation are worth knowing.
