Cyclone Map

[Ghostman]

I've always liked how tropical cyclones (hurricanes and typhoons) look like viewed from above. Although they are destructive natural disasters, there's some real aesthetic beauty to the way they spiral. So I thought that using that kind of shape as a base for a map would be interesting to try. I might use this map later for something, adding on cities and place names and borders and the like, but for now I'm just trying to create the physical geography. I'll simply call it the Cyclone Map as a working title.

I decided to use this weather radar image of the 2003 hurricane Erika, as it has a particularly nice shape to it. A radar image will be easier to transform into topography than a satellite photo would be, but comes with it's own set of hurdles.

The first challenge is to clean up the image, removing the land and ocean background and other unwanted parts, as well as reducing the blended colors into 7 or so flat discrete topographic levels. Quite a bit of manual work goes into this, mostly playing with the color-based selection tool in GIMP. I also make many small adjustments, such as separating several small islands that would have been stuck with each other or with the mainland, and connecting the two big inner seas formed between the South/East spiral arm and the center with the ocean:



As you can see, the map is very rough and pixelated from being 4x resized, and features several landlocked basins. The next step is to smooth out the rectangular sawlines in the contours, and to do so in a way that doesn't make them too regular and roundish. The coastline in particular should have some roughness to it. For this purpose I use the Distort command found under GIMP's selection menu, after selecting all the same-colored areas including their inner colors. The resulting distorted selection is sharpened and color filled, inverted and then white filled. This has to be done on separate layers for each color to avoid losing information. Thus reducing the original image to a manageable number of colors was necessary. Merging down the layers in order results in these considerably nicer looking contours:



Due to the small number of colors the topography is severely terraced. Also, the colors are based on those in the original image. Weather radar imagery uses it's own weird palette order that doesn't translate to a height map, so this calls for manual color replacement to hand-picked shades of gray, turning the map into a grayscale image. I mapped most of the heights at 10% brightness intervals, but the two highest ones to 20% brighter, thereby making the topography more gently sloped except for tall mountain areas. To remove the terracing I applied heavy gaussian blurring, re-flattening the sea level by black fill on the original coastlines selection and then blurring a bit again. Now the height map is ready to be imported to Wilbur:

[Ghostman]

The map looks pretty nice with Wilbur's texture shader. There are some very steep slopes in places where mountains range right next to the coast, but that's not a problem. The landlocked depressions at sea level are very apparent, but there are also many other basins that need to be filled:



Applying Noise, Fill Basins and Incise Flow a few times improves the topography quite a bit. Wilbur generated two very large rivers that are of immediate interest to me: the super long river that curves like a bow in a deep valley through the mainland, and the S-shaped river that snakes across a wide open plain, flowing into the inner sea. These are likely to be major waterways and cradles of civilizations:



My knowledge of Wilbur is very basic so I probably won't be getting much more use out of it for this map. If anyone has any tricks or tips to share that would be appreciated.