Change default projection type

[jwoLondon]

Now that Vega includes the equal earth projection, could It be included in Vega-Lite as one of the built-in projection types?

VL4 might also be an opportunity to change the default projection type away from mercator as this is rarely the most appropriate for the kinds of mapping Vega-lite is used for. Personally, I'd argue that the identity projection makes most sense as the default as it is semantically closest to 'unprojected' when a projection type is not specified. But if that is not suitable, the equalEarth projection would be far superior as a default compared to the mercator.

[mattijn]

I created PR #5368 to add the equalEarth as projection type in Vega-Lite.

If you want to change the default you'll have to mention this upstream at Vega. Namely, if you don't declare any projection type in Vega-Lite there is no projection declared in Vega, but the map will show up in mercator, so the default in Vega is mercator.

If it is changed there it is merely changing the docs of Vega-Lite to reflect this

[domoritz]

Vega-Lite already supports the equalEarth projection. I agree that it would be best to change the default in Vega. We can use a different default here if it's difficult to change the default in Vega.

[jwoLondon]

Ah - hadn't realised it was already there - thanks.

As for default projection, shifting the default in the Vega minor release cycle could cause backward compatibility problems, so perhaps given the VL4 major version release, this would be an opportunity to make the shift in VL independently of if/when it might happen in Vega?

[domoritz]

Yes, we could make it independently. I'd like to hear the intent to change in the next major version of Vega.

@jheer @kanitw @arvind any concerns if we change the default for v4?

[kanitw]

I was going through the list of issues and seems like this one missed the train for v4. We could still consider this for V5 though. :)