Veidrheim - Questions on Tectonics and Projections

[MrBragg]

Since I haven't seen it mentioned here yet, I'll also give a shout out to https://www.maptoglobe.com/, which makes seeing what an equirectangular map actually looks like on a sphere very easy.

[Ritterfeld]

Alright, thank you. I will look into this over the next few days. Anyhow, I still have little understanding of why and how certain factors relate to one another. For example, how come that the parallels (equator, tropics etc.) decide what kind of projection was used? I mean, I certainly didn't use any projection consciously, all I did was basically opening a document in photoshop, slapping the continents onto it and drawing lines for the "climate zones" and plates.


Actually, getting a program to paint on a sphere might be the best option for the future.

[waldronate]

In a cartesian grid on a sphere, the parallels (lines of constant latitude such as equator, tropics, and so on) are straight, never intersect, and are of different length. The meridians, in contrast, are straight, all intersect at the north and south pole, and are of the same length. Meridians and parallels always intersect everywhere at right angles.

The geometry just described only works for a sphere. To draw the map onto a plane (e.g. a sheet of paper), the sphere must be stretched out to a plane. This stretching is done via a mathematical transformation referred to as a map projection. The parallels and meridians from the sphere will assume shapes on the plane characteristic of the projection. If the parallels are straight and never intersect on the plane, and the shape is a rectangle, then the projection is of family of a projections called cylindrical projections (see https://en.wikipedia.org/wiki/Map_pr...on#Cylindrical ). The most common projection (and one that people are likely to have seen many times in their life) is a kind of navigation map called the Mercator projection. It has the property that parallels are parallel on the plane, but they are unevenly spaced.

You say that you didn't consciously use any map projection, and I agree. However, drawing what you described as a whole-world map onto a rectangle and then drawing red lines that look like parallels at increasing distance from the central line strongly suggests something akin to a Mercator projection, even if it wasn't intentional. Even if you didn't intend for the red lines to be parallels, but intended them for "climate zones", one thing that you'll find is that climate zones follow latitude because that's how sunlight is distributed on a sphere that's spinning on an axis that's tilted relative to its orbit.

The simplest way forward (not the best, but the simplest) is to keep your flat map as Mercator and accept the area distortions that get you back to a sphere. If you really need the large high-latitude landmasses for story purposes, you're going to have to do a bit of work to keep those. If you haven't invested a huge amount of effort into how things relate to each other on your map, the simplest way to try to keep your landmasses is probably to redraw them on a sphere and unproject from there.