Great Circles:
Why Your Flight Path Might Surprise You

The fastest way from
point A to B

Have you ever gazed at a map, scratched your head, and wondered why your plane from Northen Europe to the US west coast takes a detour via Greenland instead of zooming straight across the Atlantic? Well, buckle up, and allow me to demystify this seemingly counterintuitive phenomenon.

First, lets talk about the Mercator map, the trusty cartographic companion that has graced classrooms for generations. Its square grid and seemingly straightforward lines make it a popular choice. However, there’s a catch: the Mercator map distorts the true sizes and shapes of land masses, particularly those near the poles. You can read more about this in my article: Greenland vs. Africa. The true size of the world.

This distortion can lead to some surprising flight paths.
Imagine you're planning a dream vacation from Berlin to San Francisco. Consulting your Mercator map, you might draw a straight line across the Atlantic Ocean, thinking it’s the shortest path. Alas, this isn’t the case! In reality, the shortest distance between two points on Earth's surface is a Great Circle route. A Great Circle is the largest circle that can be drawn around a sphere, cutting it into two equal halves. Let's take a short look at two examples.

Canberra to Rio De Janeiro

Let's take a virtual trip from Canberra, Australia, to the vibrant city of Rio de Janeiro, Brazil. Glancing at the Mercator map, one might assume a direct flight eastward over the Pacific and South America would be the quickest route. However, the Earth's grandeur unfolds in unexpected ways.

Mercator map with straigt line drawn route from Canberra to Rio
This is not the shortest route!

The Great Circle route from Canberra to Rio de Janeiro embarks on a fascinating journey, veering along the edge of Anartica and then gently curving up along the western cost of southern america. This surprising trajectory might puzzle those relying on the flat mercator map, but it is in fact the shortest path between these two distant cities.

Globe view with Great Circle route from Canberra to Rio
The short great circle route between Canberra and Rio

So, if you find yourself soaring over unexpected landscapes, perhaps the icy expanses of Anartica, remember, it’s all part of the marvelous dance of the Great Circles guiding your way.

Berlin to San Francisco

Let's take another example. On the Mercator map, a straight line from Berlin to San Francisco seems shorter. However, the Earth is not flat, and when you map the Great Circle route, it arcs northward, passing near the Arctic Circle. This seemingly counterintuitive detour is actually the shortest distance between the two cities. Remember though, great circles are just the shortest paths to follow. In reality, pilots have to take other factors into account when planning a route, such as air currents, weather, traffic etc. So, next time you're sipping your in-flight coffee up in the skies, you can impress your fellow passengers with this nugget of geographical wisdom.
Bon voyage!

Map showing the Great Circle Route From Berlin to San Francisco
Great Circle Route From Berlin to San Francisco