List the Most Common "Reality" Errors!

[Chick]

I was thinking about creating a thread on deserts as my latest map might have one and my weakness is very much on the geographical side of things. I remembered this thread though and noticed number 8. 'Deserts form in middle latitudes, not equatorial' Perhaps that could answer some of the questions I had. Could someone elaborate on that one, please?

Due to the way the atmosphere circulates vertically, regions of the Earth around 30 degrees N and S latitudes are very dry, and regions around the equator are very wet.

http://2012books.lardbucket.org/books/regional-geography-of-the-world-globalization-people-and-places/section_04/2767c17964cb3ae62ec0e4ad304d2ef4.jpg

If you want to research why, look up "Hadley Circulation".

There are other effects due to nearby ocean currents

http://myweb.cwpost.liu.edu/vdivener/notes/gen_climate_zones.gif

but you will do just fine if you put your deserts around 30 degrees and your rainforests around 0-20 degrees.

[Chick]

LOL, I assumed the forest thing was more about scale and proportion than geography. People sometimes draw trees on their maps that tower over mountains. You don't see that much round these parts!

Yes, that is exactly the reason. It's not a geographical question, just one of drawing them. People tend to draw mountains, then they draw forests next to them, but to make the trees visible, they draw their trees as tall as the mountains.

You should try to scale your world vertically as well as horizontally

On this map (http://www.cartographersguild.com/al...chmentid=69908) I made the effort to get the trees to the right height relative to the mountains.

Here is an example of wrong proportions, although it was deliberate for this particular map (http://www.cartographersguild.com/at...2&d=1424565077), and I think you can see why it looks strange to have the trees even half the height of the mountain tops and taller than the towers in the towns.

[Azélor]

I was thinking about creating a thread on deserts as my latest map might have one and my weakness is very much on the geographical side of things. I remembered this thread though and noticed number 8. 'Deserts form in middle latitudes, not equatorial' Perhaps that could answer some of the questions I had. Could someone elaborate on that one, please?

Equatorial deserts are possible but that is not the norm. Normally it's supposed to be humid unless there is a large mountain range blocking the rain.

[Bobemor]

Ahhhh, it all makes sense now. That one more comes down to the style of your map I guess

Height of an oak tree: ~50m
Height of a mountain range: ~1000m

So your mountains need to be 20x bigger than your trees as a very very general point.
Though there are trees that would only be a 1/3 smaller than some of the smallest possible mountains xD

[Larb]

While a good guideline I think the tree thing can be a stylistic choice depending on the map. I've seen some people use big trees and make it work.

[SteffenBrand]

I'm with Larb here. As long it is a stylistic choice and not an accident, there is no problem. But keeping this in mind and remember it is important for a guide. I don't think there is a problem, but clarifying it would be good. And as always with every rule in cartography there are always exceptions. =)

[Chick]

I agree, and I did exactly that in the map I linked to as an example. All of the things in this thread can be ignored if you need to for some purpose. It's just a guide for how to make your map look realistic geographically and geologically. If, as Mark always points out, you don't care about that, then it's up to you, this is just a way to become aware of how you are changing reality.

To me, a fantasy map is ruined if it keeps me from picturing the fantasy world as real. I want the elves and dwarves to live in a world where water flows downhill. It's hard enough to suspend reality to accommodate them, without having to also suspend all the physical laws of the universe as well. I think we need to have some portion of reality to anchor fantasy. But ... that's just my opinion and everyone is welcome to theirs.

So that is really the purpose of this thread. Not to insist that everyone follow reality, but to help those who want to.

[Deadshade]

4. Mountains form in linear or gently curving ranges. Ranges don't meet at sharp angles.

To understand why this is a quite general rule, one can examine what would be necessary to get an exception.

- Mountains are created along the line of contact of 2 plates. Obviously their 2 velocity vectors being given, the ranges will be linear and sensibly parallel if there are several of them.
- The number of plates on a planet being given, there is only a very small number of points where 3 plates meet like in a T. Only in this case AND if the velocity vectors are in the right direction there could arise an exceptionnal T range form.
However the probability to find such a configuration is virtually 0 because (number of required velocity directions)/(number of possible velocity directions) e.g the probability to have a T range on a triple point location is very small.

So if the number of plates and their velocities were constant, there would almost never be ranges meeting at "sharp" angles.
However as the plate tectonics is driven by mantle convection, over very long time intervals (100s of millions years) the velocity vector of a plate may change its direction.
And when it changes, it may create somewhere a new mountain range which would still run roughly orthogonal to the new velocity but which would run in a "sharp" angle to an old range created 100s of millions of years earlier when the velocities were different.
Yet in a way even this case doesn't really contradict the above norm. As erosion works much faster than range creation, the very old range is worn down and eroded compared to the new, very high and rugged mountain range.

So the rule could be adjusted :
4. Mountains form in linear or gently curving ranges. Ranges don't meet at sharp angles unless they were created at very different times - a high and rugged new one and a low , eroded old one.

8. Deserts form in middle latitudes, not equatorial.

This one is even stronger than the 4.

It is proven that the Hadley circulation happens on every planet with an atmosphere and a rotation axis rougly orthogonal to the orbit plane. The intensity and the width of the Hadley cell can be variable but there is always one.
As this means that air rises on equator, looses humidity and goes down (around) 30° N and S we have 2 cases :
- the humidity at ground at equator is low. Then the humidity at 30° is super low and there is a desert.
- the humidity at ground at equator is high. Then the humidity at 30° is low and there is a desert.
This 30° desert will be preferentially located on the E of W side of continents depending on the planet's rotation direction.

The question whether there can't be a desert at equator is more complex.
Actually it depends on the ocean distribution.
As long as there are enough oceans in the equatorial zone, the Hadley circulation and the trade winds pretty much guarantee that there won't be deserts at equator.
However one could imagine a planet where the whole equatorial band is occupied by a continent, the oceans being mostly in polar latitudes. In this case most of the planet would be pretty much desertic.

So the rule could be adjusted :
8. Deserts always form in tropic latitudes (+/- 30°). There won't be deserts on equator if there are enough oceans on equator.

[Azélor]

This one is even stronger than the 4.

This 30° desert will be preferentially located on the E of W side of continents depending on the planet's rotation direction.

The question whether there can't be a desert at equator is more complex.
Actually it depends on the ocean distribution.
As long as there are enough oceans in the equatorial zone, the Hadley circulation and the trade winds pretty much guarantee that there won't be deserts at equator.
However one could imagine a planet where the whole equatorial band is occupied by a continent, the oceans being mostly in polar latitudes. In this case most of the planet would be pretty much desertic.

So the rule could be adjusted :
8. Deserts always form in tropic latitudes (+/- 30°). There won't be deserts on equator if there are enough oceans on equator.

That's true, deserts are more common on the western side of the continents with a normal planet rotation. I'm not sure but I think it's because the winds blow toward the west at that latitude.

[Chick]

Ocean currents near the land can have major effects, too.

http://myweb.cwpost.liu.edu/vdivener...mate_zones.gif

and keep in mind that the winds and coriolis effects are major drivers of ocean currents.