{"id":12668,"date":"2019-07-05T07:59:17","date_gmt":"2019-07-05T12:59:17","guid":{"rendered":"http:\/\/gisgeography.com\/?p=12668"},"modified":"2025-03-31T08:30:53","modified_gmt":"2025-03-31T13:30:53","slug":"great-circle-geodesic-line-shortest-flight-path","status":"publish","type":"post","link":"https:\/\/gisgeography.com\/great-circle-geodesic-line-shortest-flight-path\/","title":{"rendered":"Why Are Great Circles the Shortest Flight Path?"},"content":{"rendered":"
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\"Great<\/figure>\n<\/div>\n\n\n
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Why do you fly over Greenland in an airplane flight?<\/h3>\n\n\n\n

Or why is it that when you see flight paths on a map they always take a curved route between 2 cities?<\/p>\n\n\n\n

It’s because planes travel along the shortest route in a 3-dimensional space. <\/p>\n\n\n\n

This route is called a geodesic<\/strong> or great circle route<\/strong>. They are common in navigation, sailing, and aviation.<\/p>\n\n\n\n

But geodesics can be confusing when you’re looking at a 2-dimensional map as they follow quite the odd flight path. Let’s dig into this concept a bit deeper.<\/p>\n<\/div><\/div>\n\n\n\n

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Great Circle Routes Explained<\/h3>\n\n\n\n

In a flight path from New York to Madrid, if I asked you which line is shorter, you’d say the straight one, right?<\/p>\n\n\n

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\"Rhumb<\/figure>\n<\/div>\n\n\n

However, a straight line in a 2-dimensional map<\/strong> is not the same as a straight line on a 3-dimensional globe<\/strong>. <\/p>\n\n\n\n

This is why flight paths travel along an arc between an origin and a destination. <\/p>\n\n\n\n

Now here’s what the same flight paths look like on a sphere. Remember that the straight line in the Mercator map above followed the 40\u00b0 latitude line. <\/p>\n\n\n

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\"Great<\/figure>\n<\/div>\n\n\n

This paints quite a different story, doesn’t it? It’s deceiving to the human eye. <\/p>\n\n\n\n

The takeaway is this:<\/p>\n\n\n\n

A route that looks longer on the map is because of the distortion created by map projections<\/a> like the Mercator Projection<\/strong>. In navigation, pilots often use great circles (geodesic) as the shortest distance flight.<\/p>\n<\/div><\/div>\n\n\n\n

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Great circles vs small circles<\/h3>\n\n\n\n

Now that you have a visual understanding of great circles. Here’s a definition of what a great circle is:<\/p>\n\n\n\n