Datum for a perfect sphere?

[justlikeoldtimes]

Explain to me like I'm a kid. I'm not a cartographer. Just someone who wants to play with mapping software. What do I have to do exactly?

My only concern is making a world map in various projections, mixing and matching what I like. I have a input data/image I want to use: a topographic map with the plate carrée projection, with a resolution of 3840x1920. It's exactly twice as wide as it is tall.

For now, I'm only going to entertain myself with map projections that have the 2:1 ratio. I would like the outputted images to have the same exact resolution. I'm already making sure my maps do not have an outer boundary, to ensure I have the exact desired resolution. I can tolerate the margins between the map proper and the document bounds, because I can just open up the exported image and crop them in Photoshop.

I know the real Earth is not a perfect sphere; thanks to the rotation of the planet, measuring it around the equator will be a bit longer than it is around north/south. Perhaps when I mature as a map enthusiast, I will account for this when creating maps I want to see. But not for now, I'm putting that thought to the side. I'm currently fixated on geometric elegance.

What exact settings in Datum should I enter to ensure that I still get a 3840x1920-sized image? Not 3842.103x1920, etc. It's driving me nuts. Do I just need to experiment around more?

[Atarimaster]

I would like the outputted images to have the same exact resolution.

Well … Why?
The thing is, it’s complicated and I’m not sure if it is possible at all.
See this instructions given by daan, which refer to a somewhat different task and therefore, may not apply to your wish.

So in most cases, it’s better to put up with the fact that you can’t set a map’s size exactly, down to single pixels. Saves time and nerves.
(I think there’s another thread where daan explains why this is so hard, but at the moment I couldn’t find it.)

Sorry that I can’t help here.
Kind regards,
Tobias

[justlikeoldtimes]

Thanks for the reply. Sorry if I came off as too impatient. lol.

I'm trying to create some sort of satisfying animation between various projections.

[daan]

Tobias, many thanks for looking up that old post. Hopefully it answered the question.

— daan