Benvenuto nel Poliverso

Mina

2 mesi fa • •

Mina
2 mesi fa • •

We all know, how crappy the common #Mercator projection for world #maps represents areas, inflating them with distance from the equator.

What many people don't know, is why this projection is still so popular:

The shortest path between two points on the globe, is a straight line on the map.

I reckon, this is useful.

In all other projections, the shortest paths are curves.

In #Maths, we say, the Mercator projection preserves angles, not areas.

A world map. Countries are drawn in light blue according to the Mercator projection. Inside, in darker blue the actual sizes of the countries.

Especially in the cases of Alaska, Canada, Greenland and Russia, the real area is only a small fraction of the apparent sizes.

Mike reshared this.

in reply to Mina

The Mercator projection does preserve angles, but that doesn't mean it sends shortest paths to straight lines. There is a projection that does that, the Gnomonic projection (en.wikipedia.org/wiki/Gnomonic…).

map projection

^{Contributors to Wikimedia projects (Wikimedia Foundation, Inc.)}

in reply to Oscar Cunningham

Mina

in reply to Oscar Cunningham • 2 mesi fa • •

@OscarCunningham

I knew, someone would come up with this.

True: The shortest distance between two points on a smooth manifold is the geodetic, which is in the general case not exactly a straight line in the Mercator projection.

However: Before GPS, if you wanted to plot a course for your ship or plane, you would determine the right angle to the pole and then keep it.

For not too long distances, this straight line on the Mercator map is close enough and, most importantly, easy to follow.

@Oscar Cunningham

in reply to Mina

Nerd

in reply to Mina • 2 mesi fa • •

Errrmm...
Hate to have to say it - but I think you are wrong.
(z.B. blauwasser.de/grosskreis)

[Or did I not get the irony somewhere?]

in reply to Nerd

Mina

in reply to Nerd • 2 mesi fa • •

@Nerd

Check, what I previously wrote:

berlin.social/@mina/1148179406…

Mina

2025-07-08 13:52:17

@OscarCunningham
I knew, someone would come up with this.
True: The shortest distance between two points on a smooth manifold is the geodetic, which is in the general case not exactly a straight line in the Mercator projection.
However: Before GPS, if you wanted to plot a course for your ship or plane, you would determine the right angle to the pole and then keep it.
For not too long distances, this straight line on the Mercator map is close enough and, most importantly, easy to follow.

@Nerd

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