View Full Version : How do I determine my sizes for a world?

09-19-2010, 08:05 PM
I am currently in the process of creating a earth-sized world and I am needing to know what should my image size be? Looking at most world maps, they are more rectangular than square, so i am thinking that square isnt the way to go. Also, it seems like there should at least be some sort of polar/ice cap section on each of the poles.

The world will be rather water-filled, lots of islands with 1-3 larger landmasses.

So, I was thinking that i read somewhere around here that to make the earth, you would need something like a map size of around 25000 x 25000 pixels, but that seems rather too ridgedly squarish compared to other world maps.

09-19-2010, 08:22 PM
You'd need a map roughly 25,000 x 12,500 where the width is twice the height. This let's the image wrap to a sphere nicely. It also assumes that 1 pixel = 1 mile at the equator. The earth itself is between 24 and 25 thousand...you can Google it up for accurate numbers. How big do you make your map? As big as you need to in order to convey the information that you want to convey. Therefore, it isn't totally necessary to make an image that large unless you want to show a lot of detail. I could make a world at 6,000 x 3,000 and convey a lot about the terrain plus labels and roads and all sorts of stuff. Or you could make a bunch of smaller maps then stick em all together at the end.

09-19-2010, 10:06 PM
Thanks! Thats helps quite a bit.

09-20-2010, 03:19 AM
Or do it in vector and forget about all this pixel crap ;-)

09-20-2010, 07:48 AM
It depends on the projection.

Equirectangular is popular in 3d graphics and is simple to understand. Vertical distance is proportional to latitude (and north-south distance), and horizontal distance to longitude. If they use the same scale factor, then it's twice as wide as it is tall for a full globe. This projection produces lots of horizontal distortion near the poles though and is rarely used for the final presentation of maps.

Normal Mercator is a good option. It preserves directions and at large scales, preserves shapes. However, sizes are distorted. The closer to the poles you get the bigger things are. It also has the problem of being unbounded vertically. (Effectively, it needs to be 'infinitely tall') So you have to cut off the poles and handle them separately. Apart from that, it's probably easier to deal with in terms of drawing continents. It was created for early ocean navigation, and was later used for global reference maps (Atlases, etc). It has largely been replaced in both roles though it is used a lot in web cartography (Google, OSM, etc). Your best option is to start with a graticule template (The grid of longitude and latitude lines).

Robinson and Winkel Tripel are two modern global reference projections. They strike a balance between preserving different factors while distorting all of them a bit. They aren't as amenable to drawing on as Mercator, and have a rather 'modern' look to them, but they really are good at conveying the overall layout of a world. Even more so than Mercator, you'd want a template to try to use these directly for drawing.

The 'best' option would be to work out roughly where each continent is, create a specific projection for each (Probably using a Planar, Conic, or Transverse Mercator projection), draw the continent in that projection, then convert each to geographic coordinates/equirectangular and combine them, then project to a global reference projection or regional projection for display. Obviously, this is a fair bit of work and requires some extra software that can reproject the maps. If you didn't follow all that or it seems way overkill, then don't worry and just ignore it.