Have you ever looked at Google Maps and noticed that Greenland appears absolutely enormous—almost as large as the entire continent of Africa? Yet if you check the actual numbers, something doesn’t add up. Greenland covers approximately 2.17 million km², while Africa spans a staggering 30.37 million km². That means Africa is roughly 14 times larger than Greenland, yet on most web maps, they look surprisingly similar in size.
So what’s going on here? The answer lies in a fascinating piece of mathematical cartography called the Web Mercator projection.
What is the Web Mercator Projection?
Web Mercator, officially designated as EPSG:3857, is the standard map projection used by virtually every major web mapping service you’ve encountered, including Google Maps, OpenStreetMap, Bing Maps, Apple Maps, and countless others. It’s the reason your online maps look the way they do.
This projection is based on the classic Mercator projection created in 1569 by Flemish cartographer Gerardus Mercator. Originally designed for nautical navigation, it helped sailors plot straight-line courses across the ocean—a revolutionary tool for 16th-century exploration.
The Core Problem: Conformal vs. Equal-Area
Here’s the fundamental issue: Web Mercator is a cylindrical conformal projection. Let me break down what that means:
Conformal means it preserves angles and shapes locally. If you’re looking at a city block or planning a route, the shapes look correct and north is always “up” on your screen.
However, this angle preservation comes at a significant cost: severe area distortion, particularly as you move away from the equator toward the poles.
The Mathematical Culprit
The distortion isn’t just a quirk—it’s built into the mathematics of the projection. In the Mercator formula, a point at latitude φ (phi) is projected vertically as:
y = ln(tan(φ/2 + π/4))
Where ln is the natural logarithm and tan is the tangent function.
Here’s where things get interesting (and problematic): As you approach 90° latitude (the North or South Pole), the tangent of 90° approaches infinity. This causes infinite vertical stretching at the poles.
That’s why Web Mercator actually cuts off at approximately ±85.05° latitude—the projection literally cannot show the poles because the math breaks down. Try zooming in on Antarctica or the Arctic Ocean on Google Maps, and you’ll notice the map eventually stops.
Greenland’s Deceptive Size
Greenland sits between 60°N and 83°N latitude—right in the zone where Web Mercator distortion becomes dramatic. At these high latitudes, the projection stretches the island vertically and horizontally, making it appear far larger than its actual size.
Let’s look at some real comparisons:
- Greenland: 2.17 million km²
- Africa: 30.37 million km²
- Brazil: 8.51 million km²
- India: 3.29 million km²
- Algeria: 2.38 million km²
Africa is 14 times larger than Greenland, Brazil is nearly 4 times larger, and even Algeria (a single African country) is bigger than Greenland. Yet on Web Mercator, Greenland often appears comparable to or larger than all of these.
Other Victims of Mercator Distortion
The same mathematical distortion affects many other regions:
Antarctica appears as an impossibly massive stretched strip along the bottom of maps, when it’s actually about 14 million km²—smaller than Asia or Africa.
Alaska looks disproportionately large compared to the continental United States. In reality, Alaska is 1.72 million km², while the lower 48 states combined are about 8 million km².
Scandinavia appears larger than India, though India is actually more than three times bigger.
Equatorial countries get shortchanged. Nations near the equator like Indonesia, Brazil, and the Democratic Republic of Congo appear smaller than they really are because there’s minimal distortion at 0° latitude.
So Why Do We Still Use Web Mercator?
If Web Mercator distorts area so badly, why is it still the standard for web mapping? The answer is that it has several crucial advantages for digital mapping:
1. Preserves shapes locally – When you’re zooming in on your neighborhood or planning a driving route, buildings and streets look the correct shape. The angles are accurate for navigation.
2. Mathematically simple and fast – The projection calculations are computationally efficient, which matters when rendering millions of map tiles for users worldwide.
3. Easy to tile for zoom levels – Web Mercator creates a perfect square map that can be easily divided into tiles at different zoom levels. This makes the familiar “zoom in/zoom out” experience smooth and seamless.
4. North is always up – The projection preserves cardinal directions, making it intuitive for users to orient themselves.
5. Works well for local navigation – For the most common use case—finding your way around a city or region—the distortion is minimal and the preserved angles are essential.
Alternatives: Seeing the True Size of Countries
If you want to see the actual relative sizes of countries, you have several options:
Equal-area projections like the Gall-Peters projection, Mollweide projection, or Equal Earth projection preserve area, showing countries at their true relative sizes (though they distort shapes instead).
Interactive tools like thetruesize.com let you drag countries around the map to see how their size changes with latitude, demonstrating the Mercator distortion effect in real-time.
Physical globes remain the only perfectly accurate representation of Earth’s surface, with no distortion of either area or shape (though they’re not exactly practical for turn-by-turn navigation).
The Fundamental Truth About Map Projections
Here’s the key takeaway: Every map projection is a compromise. You simply cannot project a sphere onto a flat surface without distorting something.
The brilliant mathematician Carl Friedrich Gauss proved this with his Theorema Egregium (Latin for “Remarkable Theorem”) in 1827. You must choose what to preserve and what to distort:
- Conformal projections preserve angles but distort area (like Web Mercator)
- Equal-area projections preserve area but distort shapes and angles
- Equidistant projections preserve distance from certain points but distort everything else
- Compromise projections try to minimize all distortions but don’t perfectly preserve anything
Web Mercator chose to preserve angles and sacrifice area accuracy. This makes it perfect for navigation and local wayfinding—which is exactly what Google Maps and similar services are designed for—but misleading when trying to understand global geography, compare country sizes, or analyze global phenomena.
Educational Impact and Geographic Literacy
The widespread use of Web Mercator has real educational implications. When people primarily encounter world maps through Google Maps and similar services, they develop a skewed mental model of global geography.
This can affect:
- Understanding of geopolitical scale and importance
- Perception of climate zones and their extent
- Appreciation of developing nations’ true size and significance
- General geographic literacy and spatial reasoning
Many educators now advocate for using equal-area projections when teaching world geography and reserving Mercator-style projections specifically for navigation contexts.
Practical Tips for Map Users
When using web maps, keep these tips in mind:
- Remember the distortion increases with latitude. Trust the map near the equator; be skeptical near the poles.
- Use equal-area projections for size comparisons. If you’re comparing countries, regions, or global phenomena, find a map that preserves area.
- Check actual statistics. When size matters, look up the actual square kilometers rather than relying on visual comparison.
- Use Web Mercator for what it’s good at. For navigation, route planning, and local exploration, Web Mercator is excellent.
- Educate others. Share tools like thetruesize.com with friends to help build better geographic intuition.
Conclusion
The next time you open Google Maps and see Greenland looming large on your screen, you’ll know the mathematical reason behind the illusion. Web Mercator’s infinite stretching at high latitudes transforms Greenland from a large island into an apparent continent.
This isn’t a flaw that needs fixing—it’s an intentional trade-off. Web Mercator sacrificed area accuracy to give us the navigational tools we use every day. Understanding this compromise helps us become more informed map readers and more geographically literate global citizens.
The key is knowing which tool to use for which job. Web Mercator for navigation, equal-area projections for geographic understanding, and always a critical eye toward the distortions inherent in any flat representation of our spherical world.
I hope this tutorial will create a good foundation for you. If you want tutorials on another topic or you have any queries, please send an mail at contact@spatial-dev.guru.