April 18, 2018

A Question of Scale

One problem I see popping up in a lot of fantasy maps is the scale of features on the map. Maps which purport to show areas the size of Russia have four major cities, one big river, and a few clearly marked mountains.

That's just not the case for real-world geography. There's a lot of stuff in the world. There's a really high chance that your map should be stuffed full of cities and other human effects. My map currently plans to cover approximately 37 million square miles (Earth is around 57.5 million).

Averaging terrain into 20-mile hex blocks also doesn't quite fall out how I expected. This became starkly obvious when I was working with the height maps. At that time, I was placing hexes in 1000 ft increments. But if you think about it, 1000 ft over 20 miles is about half a degree of slope. You wouldn't even notice that. It certainly doesn't qualify as a mountain.

A 20-mile hex has an area of about 346 square miles. Conveniently, this is close to the base area of Mt. Everest. Now, Everest does not rise straight up from sea level, but let's imagine it does. If we imagine this mountain as rising from sea level to 26,000 ft inside a single hex, that's an average slope of only 26 degrees! And that's just calculating using the highest point. Even if we use the average (13,000 ft), then Everest would appear on our map suddenly jut up from our plain, and the 20-mile hex map would deceive us as to its actual height. A mountain slope is usually (but not always) around 30-35 degrees.

That really changes my perspective on how mountains look on a height map. If you look at a hex-binned height map of Earth, you can tell where the "high places" are, but not necessarily individual mountains. The following picture is a 20-mile hex map (roughly) of Earth's topography in North Italy and the Alps. Sorry about Genoa, it got wiped out when I processed the image in Gimp. Data from here. As you can see, the real topography is barely discernable from the 20-mile hex averaged height. Le Mont Blanc (15,777 ft) isn't even the highest hex here. Nearest I can tell, the highest hex here contains Ă„ussere Schwarze Schneid (10,686 ft) among others. It's very interesting that there are so many mountains packed into here that just plain don't show up.

Let's get back to definitions. Mountains are pretty roughly defined. As I was researching the slope numbers above, I remembered that Olympus Mons, the highest mountain in the Solar System, has a slope so gentle you probably wouldn't notice if you were walking up the side (this is not so different from the outskirts of many shield volcanoes on Earth). It's also extremely huge, not only in height but in area. It would nearly cover France! I've seen many fantasy maps with similarly sized mountains.

None of this is necessarily a problem. It might be good enough to define "mountainous terrain" for the purposes of the world map. But individual peaks might be more difficult to place. 346 square miles is a lot of area for those peaks to appear in. That might be a problem to save for the 1-mile hex project in a few years.

The elevation affects base temperature, precipitation, and travel time (important for trade routes). Therefore, figuring out the best way to create and describe it numerically will be important.

I used the Hexagonize Script for GIMP to create the hex maps from the height data.

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