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Mercator v Reality
(i.imgur.com)
With a human face
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this post was submitted on 06 Sep 2024
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Dln't quote me on this, but from what I've heard, the Mercador projection became standard because it's good for navigating since qit conserves angles. Draw a strait line depicting your current trajectory and another the trajectory that would get you where you want, measure the angle between them, and that's the actual angle you need to turn.
Yeah, it’s actually a really great map for its purpose of navigation, which is a pretty damn important aspect of map usage. I’m tired of everyone shitting on it because of that scene in west wing.
It’s great for navigating at sea, but bad for looking at the world as a whole. Nowadays most people use maps for the latter; hence the complaints.
Sure, that’s why I qualified with “for its intended purpose”. It’s not a great classroom map but it is perhaps the most historically important projection. The problem is this idea of “Mercator bad” has entered public consciousness. For example, the start of this thread mentioned “how not-great the mercator is” without any such qualifications.
Maybe one day I’ll get a Cahill-Keyes projection on the wall. I think it’s useful to see how surface areas compare.
Which scene is that?
https://youtu.be/vVX-PrBRtTY?si=EJI98A0zZR6zkURc Im sure there were people who felt this way before this episode, but it really exploded in public consciousness afterward.
Internet people pretending to have never seen a globe at school so they can be outraged by Big Greenland.
In the Internet age, I believe Mercator remains standard because it's easy, since image buffers and UI viewports are implemented as rectangular arrays. For example, when you click on the map the pixel coordinates can be converted to (lat, long) just by scaling, without having to do complicated coordinate transformations.
What you see in stuff like Google Maps or OpenStreetMap isn't plain Mercator, it's a variant called "Web Mercator"
And the US DoD doesn't like it because it introduces even more deviations than plain Mercator.
It's all about your intended use. If you want to use Google maps to get to work, the DoD has no problem with web Mercator on the maps backend that serves up your map tiles.
If you're firing up Arcmap for a GIS project, using the map to navigate based on earth features, or making a reference map, of course the DoD or anyone else, wouldn't want you to use web mercator
And no projection is perfect they all introduce weird things, like this equirectangular map
which is not conformal or equal area.
This one has been mentioned a few times: https://en.wikipedia.org/wiki/Kavrayskiy_VII_projection