[adim86]

I find it shocking that a reputable resource such as this is still displaying the size of Greenland or Africa wrong (Mercator projection) in relation to other land masses in its marketing material and documentation, like here. It just brings doubt to the whole project, which is a shame considering all the time they must have put in. Why show the map that way when majority of its users will never use it for nautical navigation? https://maplibre.org/maplibre-gl-js/docs/examples/display-a-...

[dan-robertson]

I’m not sure it’s very useful to rehash an argument with very tenuous relation to the OP here. The normal reason to use the Mercator projection in these situations is (a) it’s what people are used to and (b) it preserves angles so if you zoom in on a street then up will still be north and roads that are at right angles in the real world appear to be at right angles on the map. The latter property is pretty desirable and hard to achieve without doing some weird transition between projections as you zoom. This matters more for Europe (and I suppose parts of British Colombia) where there is a high population density at latitudes that are pretty extreme in much of the world.

I think Apple Maps has a pretty reasonable compromise here of transitioning from a globe to Mercator as you zoom, but this is a less nice UI with a mouse as you need to click to rotate the globe instead of pointing and zooming only. I don’t think there’s anything in this data that would make that unachievable – you just need to reproject the vector data a bit as you zoom out – but it takes some tricky mathematics to get right and so hasn’t been done yet.

[willtemperley]

It's an important discussion because it's abundantly clear that almost nobody on this thread has a clue what they're talking about.

Web Mercator != Mercator.

I suggest most people on this thread need to go away ask the question "What's the difference between Web Mercator and Mercator".

[Symbiote]

For most uses of web maps (navigation on foot, by bicycle or by car) the angles seem to be close enough with Web Mercator, and the map is zoomed in to a small area so there's no concern about the area.

No-one is zooming out the "Find your nearest Tesco" map to see Greenland.

[dan-robertson]

If two lines are at right angles in the ground and, say, outside the arctic/antarctic circles, what range of angles might be between them in a web Mercator projection?

[dzogchen]

It's on our roadmap to support alternate projections, but as you can imagine it's a big project that so far nobody has been willing to pay for to implement unfortunately.

MapLibre GL JS does support globe mode. https://maplibre.org/maplibre-gl-js/docs/examples/display-a-... May we should update our examples to use globe mode when showing examples, especially those that show a world map. We will take that feedback into consideration!

You can use the Equal Earth projection with a plugin: https://equal.bbox.earth/maplibre-americas/

[readyplayeremma]

MapLibre's globe mode is both fantastic and performant. Also, it's literally just the one option to change it, and your tile formats/CRS don't need to change either.

It's the easiest way to escape from web mercator projections with no real downsides that I have discovered yet. Also, there is a built-in control if you want to offer a button to toggle between web mercator view, and globe view, since it's all just rendering changes.

[mourner]

You can read more about why most web maps are like this and a quest to fix this in this article: https://www.mapbox.com/blog/adaptive-projections

[workmandan]

Web Mercator is the standard projection used on the web, if you think the we should use a different projection on the web then that's a completely separate argument

[willtemperley]

It's actually worse than that because the Web Mercator projection is unusable for navigation too - it doesn't preserve angles or area! (Angles are nearly preserved).

Well done Google. Slow handclap.

The NGA advised it's likely to cause geolocation errors of up to 40km near the poles:

https://www.gpsworld.com/nga-issues-advisory-notice-on-web-m...

[Flatterer3544]

You're a bit hasty, for the users that needs mercator projections, they should be able to get it, see: https://maplibre.org/maplibre-gl-js/docs/API/type-aliases/Pr...

[bottled_poe]

Accuracy where it matters is why. Do you have a better suggestion for projecting a sphere onto a rectangle?

[einpoklum]

I would not use such strong rhetoric as the GP, but I believe they probably mean we should lean towards using the Gall/Peters projection, which maintains lengths and areas, but not angles.

(There are of course other projections with other interesting features; or you could take the same projection but center the world differently etc.)

[willtemperley]

Web Mercator does not preserve angles.

We're currently forced to use a projection that is strictly worse than what it was based on, the Mercator projection, created in 1569.

Everyone on this thread needs to read this presentation entitled "Use Literally Anything But Web Mercator":

https://www.esri.com/content/dam/esrisites/en-us/events/conf...

Let's say that a bit louder shall we:

USE LITERALLY ANYTHING BUT WEB MERCATOR.

[einpoklum]

Thanks for that, I wasn't even aware that "web Mercator" was a thing.

[ecshafer]

Why? Why is lengths and areas more important than angles? You have to choose one, its essentially arbitrary. Personally I find it more useful to know what is parallel to what and what is at which angles from what, than some size. We have globes, so we know what the "real size" of Greenland looks like... this has always been a silly argument from the overzealous online looking for right wrongs that don't exist.

[einpoklum]

> Why is lengths and areas more important than angles?

Well, of course the answer is "it depends on what it is you want to learn from the map. If you're driving around and want to navigate, you'll take Mercator probably. But if you want to compare sizes of objects (like lakes or forests or islands or world states), especially when zoomed out, you'll prefer Gall-Peters.

Many argue, and I tend to agree, that when looking at a map of the whole world, you are typically better served with Gall-Peters in terms of what your interest is, and in fact, people _do_ use Mercator maps to semi-consciously compare sizes of things - and have false impressions about geo-politics because of it.

[willtemperley]

WEB MERCATOR DOES NOT PRESERVE ANGLES.

[ecshafer]

I know. But they mentioned Mercator, not Web Mercator.

[willtemperley]

They were talking about Web Mercator but didn’t know they were!

[willtemperley]

This comment is inaccurate! Web Mercator causes such large errors in geolocation that the NGA had to issue an advisory about it [1].

There is a whole science behind map projections and Google ignored it entirely when they created Web Mercator, which was a hack to divide the world into a quad tree. It was vaguely clever and utterly stupid at the same time.

[1] https://web.archive.org/web/20140607003201/http://earth-info...

[willtemperley]

> Accuracy where it matters is why

Why the downvotes for correcting this laughable statement? Web Mercator is well documented as being extremely inaccurate.

[mmooss]

Hi - I understand you feel strongly; your Web Mercator input is interesting. I would just focus on the intellectually interesting part - people might not get it; you can't control that or compel them to.

You've been repeating essentially the same comment, writing in all caps (in some comments), complaining about downvotes, telling everyone they are idiots one way or another. None of those things are likely to be welcome.

[willtemperley]

Almost every commenter here repeated the same misconception, and I corrected them each time.

I feel justified in shouting in this case.

[trgn]

Web mercator is fantastic map. It's well known of course, so very helpful to orient. Plus, its square and easily tile-able, which is good for performance. Shapes of countries are preserved. Plus, the lines are straight, which works great for on screen. Neat and tidy.

Who cares Greenland looks big when zoomed out. "Mercator distorts size" is one of those gis-nerd idee fixes, the first factoid they learn in class, and it overwhelms all thought.

[mmooss]

> Who cares Greenland looks big when zoomed out.

You never know - one day, the geography of Greenland could matter quite a bit to the rest of the world.

[fragmede]

Maybe you shouldn't have skipped that class if you don't think it's important.

[lars_francke]

Because that's what everyone is used to.

Maplibre supports different projections if you want.

[techterrier]

obligatory West Wing: https://www.youtube.com/watch?v=vVX-PrBRtTY

[ecshafer]

This episode never made any sense at all. We already have globes for true sizes.

[xigoi]

Not everyone has a spherical monitor.