Long story short, I got to thinking about rendering a global map in hexes, using the hex templates I already created. If you're interested in hexing out your campaign world and are only mildly bothered by inaccurate polar distortion, here's an approach you might want to consider.
If you're already familiar with the Welsh Piper's hex templates, you can skip this section. Otherwise, here's the rationale I put behind the World hex template:
The Atlas map (at right) is a 625-mile square divided into twenty-five 125x125 mile blocks. Each of these blocks is, in turn, represented by a single Regional map. The hexes on the Regional template can themselves be detailed on the Sub-hex template; you can then rescale the Sub-hex template to zoom into smaller and smaller areas. In short, you can go from a 25-mile Atlas hex all the way down to a 0.2-mile sub-hex and, with very little effort, maintain relatively precise positioning and scale.
The World hex template just scales in the other direction, being composed of several Atlas templates. Now you can start with a global view and zoom all the way into a 0.2-mile sub-hex pretty easily (and by easily, I mean without getting out a ruler or a calculator or actually doing anything but a bit of simple math in your head).
Creating the Template
The concept is pretty simple: arrange Atlas maps on flat surface to represent a globe. Question is: how many and in what arrangement? Again, my OCD compels me to show my work, but if you don't care how I came up with the template, feel free to skip ahead.
Starting with an equirectangular grid (shown below), I let climate dictate size: To keep things simple, I use five climate bands (from pole to equator, that's arctic, sub-arctic, temperate, sub-tropical, and tropical). For convenience, each band spans a single Atlas map (i.e., each climate type ranges 625 miles north to south). As a result, there are 5 Atlas maps above and below the equator. This makes the map 6,250 miles from north to south.
The proper aspect ratio for an equirectangular grid is 2:1, so given 10 Atlas maps from pole to pole, I put 20 Atlas maps along the equator. This gives an equatorial circumference of 12,500 miles.
With the grid established, I determine the placement of Atlas maps. Each of the white blocks on the template above is a single Atlas map (the grey areas are unused). Token acknowledgment of polar distortion is achieved by gradually reducing the number of Atlas maps toward the poles.
Given the above, you'll end up with a world with an equatorial circumference of 12,500 miles. The distance from pole to pole is 6,250 miles (3,125 miles from equator to pole). Each Atlas map is a 625-mile square, with an area of 390,625 square miles. The distance along each edge of an Atlas map spans 18° of longitude (north/south) or latitude (east/west).
Using the Template
World creation with the template is very easy with these instructions:
PNG - the World template PNG is good for inserting into your favourite image editor or graphics program.
Start mapping: draw your world's coastlines and prominent features right on the template. Ddraw only on white blocks, and remember to "wrap" the hemispheres (e.g., the eastern edge of block I3 overlaps the western edge of block L3).
Drill down: use an Atlas template to detail blocks on the World map; I suggest using the World map's coordinate system to label individual Atlas maps
That's pretty much it.
Two areas of concern occur to me about the template. I'll do my best to address them; as always, your comments and suggestions are welcome.
The first is that the world template isn't very big. In fact, the equatorial circumference is half that of Earth's. Not having bothered to research such things, I don't know how this affects the planet's rotation, atmosphere, the length of a day, or the planet's surface gravity. While these are important scientific details, you can probably just assign whatever parameters you want and be done with it. If you want a 24-hour day and a certain axial tilt and gravity of 1G, simply make it so. Unless you're playing a sci-fi game, it's not likely that your players will question these details or even ask about the planet's size.
Similarly, as a GM, you may have concerns that the world is too small to accommodate all the different settings you want to add. Valid point, though I submit that worldbuilders often err on the side of Too Beaucoup. Trust me when I say that 60 Atlas maps per hemisphere is a lot of real estate (over 23 million square miles, actually). Aside from the fact that this would take more time than a busy GM has to map out and detail, the scope of most campaigns suggest that your PCs will probably experience only a fraction of what the world has to offer.
If you actually run out of space, use the template above, but double the span of each climate band. This gives you an Earth-sized planet, so you could easily mimic real-world geography and weather patterns. (Thinking on it, you could also reverse this, and make a small moon with just Atlas templates...more on that later, I think.)
The second concern isn't really an issue (to me), but I feel compelled to mention it: The World template is nothing close to precision cartography, particular as it pertains to wrapping an equirectangular grid around a sphere and calling it a planet. In fact, I can assure you that I pretty much ignored the math of it. Recklessly, one might say. So if you decide one day to cut out a paper copy of the World template and make it into a ball, you risk disappointment upon realising that the misshapen wad of paper in your hands looks nothing like the campaign setting you've lovingly crafted.
But I think that's OK because the template does a pretty good job of straddling the line between "reasonably accurate" and "this is fun!". I can also assure you that if your players are seriously concerned about the precision of longitudinal distance at high latitudes, they should be reprimanded for meta-gaming or subtly encouraged to suspend their disbelief. (Again, unless you're playing a sci-fi game, the issue probably won't come up. And if you are playing a sci-fi game, chances are you're not really mapping the entire world anyway, so you can probably fudge it just fine.)
The benefit of this approach to world cartography is that you can use an existing body of hex templates (without modification) with a template that provides a lot of world specs that often go undefined (e.g., climate bands, longitude, circumference). There's also a built-in adjustment for distance at high latitudes. Best of all, you get to use hexes--how is that ever anything but a plus? Happy mapping!