How-To: Hurricane Map
Hey, great news! I've made a step-by-step video showing you how to make this map. Check it out here.
Here's a run-down with all the carto nitty-gritty on how to make this map in ArcGIS...
It shows the locations of each recorded hurricane and tropical storm since the mid 1800s. When viewed in aggregate, the hurricanes appear to coalesce into a single great hurricane eye. It’s a basic map, with some cartographic punch. Super simple to make yourself. I’ll give links to all the data and icons, and provide a step-by-step on how to smash them together.
Batten down the hatches.
Data & Resources
Here are some resources that you can download, if you’d like to follow along.
NASA basemap image (zip download option with image and projection files, ~22MB). You have to love the work of the NASA Visible Earth team, and that they make their beautiful and useful products available to us all. I downloaded one of their global cloud-free satellite images, then georeferenced it so that it could (and would) be monkeyed around with in various projections. Alternatively, you can also link directly to the World Imagery service (a live feed of high-res, up-to-date satellite and aerial imagery) or turn on the "world imagery" basemap. If you go this route, just skip the section where I de-saturate the basemap and set the layer transparency to 80%.
NOAA historic hurricanes (zip download option with six shapefiles, ~7MB). Sourced from the NOAA's National Centers for Environmental Information, these six shapefiles represent the best known historical locations and magnitudes for historic hurricanes and tropical storms. These shapefiles are segregated by Saffir-Simpson hurricane categories 1-5 (and tropical storms).
Coastlines and graticules (link to Natural Earth’s data-download page). These came straight from Natural Earth, a great resource for basic, commonly-needed shapefiles for map making. Here are the direct download links to the Coast shapefile and the 20-degree graticule shapefile.
Firefly Icon Images (zip of six PNG images, ~7KB). Don’t feel tied to the default pack of symbol markers in your GIS. You can use your own images -which is a lot of fun. This set of glowing-dot images will be used to represent hurricane strength.
That’s it for downloads, you have all the parts you need (assuming a tenacious curiosity and 10-15 minutes).
The Right Projection
The best visualizations never celebrate the data; instead they make us learn about worldly phenomena and forget about the data. -Kirk Goldsberry
Let's take a look at that basemap image and hurricane data to see if there's a map projection that best communicates something interesting, so that we can forget that this is data but rather a whooshing mega-pile of hurricanes...
The de-facto coordinate system for shared GIS files is WGS 84, which projects into this vanilla equirectangular, or Plate Carree, view.
Promise me, on everything you hold dear, to never leave your published map in this projection.
Anyway, check out that pattern!
Hurricanes carve a well-worn belt right around the planet. A band in the Northern Hemisphere and a band in the Southern Hemisphere.
Lets look for a projection that better illustrates that ring-edness...
This top-down perspective showcases the circuitous nature of hurricanes well.
Unfortunately, most of the action happens in the Northern Hemisphere, which has some cramped quarters in this North Pole Stereoscopic projection.
What if we flip it?
Ohhhhh yeahhhhh...
Here is a South Pole Stereographic Projection. This bottoms-up view of Earth highlights the circular structure of the hundreds of hula-hooping storms, while maximizing the real estate of the denser Northern Hemisphere.
This projection also gives us a nice recursive sense of aggregated hurricanes forming their own radial hurricane structure. A storm of storms.
Basemap
Now that we've got the projection in place, it's definitely time to give that satellite basemap some attention. While beautiful, the one and only job of this imagery is to provide some spatial context for the reader. Where am I looking? As such, this high-saturation, high-contrast, image overpowers the hurricane events and steals from the focus of the map. Because our hurricanes are going to be bright and colorful, the basemap helps to promote them by being darker and de-saturated.
One straightforward way to do this is to add two copies of the satellite imagery to your map. The bottom-most version is the standard full color, set to RGB:
Which looks like this:
On the upper-most version of the image, apply a "stretched" symbology with a black-to-white color ramp:
Giving us a gray-scale image, like this:
Then, apply a slight transparency to this gray-scale image (8 - 10% transparent), so just a bit of the color of the lower image comes through. A cheap trick, but it results in a powerful basemap image, ready to stage some vivid data.
Icons
Everything is related to everything else, but near things are more related than distant things. -Waldo Tobler
Anyone who’s been in or near a hurricane can tell you that a rigidly precise flat symbol like a point or a line isn’t necessarily true to the broad, fuzzy-edged nature of a moving storm. Using a symbol with a blurry edge helps illustrate Tobler’s First Law, plus I think it looks really cool. I call it firefly cartography. Glowing bright symbols over a dark basemap. You can call it whatever you want.
Notice how they have a white-hot center, and only the glow effect has the color encoded?
Lucasfilm
Lucasfilm
Not as clumsy or as random as a flat icon. An elegant symbol... for a more civilized age.
Lets reach out to these glowing point images for our hurricane point icons. For each hurricane category, link it to the corresponding PNG image. You can tweak the size of the icon to an overall density that looks best to you. Just avoid scaling it up higher than the image’s native resolution or else you could get some pixelation.
Raw points as flat symbol markers...
Points using glowing symbols, tiered by severity...
Composition
The heavy lifting on this sucker is done. Now all there is to do is add in some minor shape details and soften the hard-edges of the layout with a vignette...
Lets turn the hurricanes off temporarily and get to work polishing up this basemap.
Adding in a coastal reference goes a long way towards giving map readers some bearing when looking at an unusual, bottoms-up, perspective of the world. I gave mine a very thin width, an earthy color of 255, 211, 127 (rgb), then set the layer to 80% transparent.
For some reason, faint graticule lines provide a sense of order and cinematic coolness. These lines are a cool slate color of 0,132,168 (rgb), and set to 70% transparent.
Because the concept of the equator is so important to the nature of hurricanes, it deserves a place in the layout.
I used the same earthy color of 255, 211, 127 (rgb) to help contrast it from the hurricane points, and pushed it back to 70% transparent.
It also has a dashed effect to help illustrate that it is a reference, and not an actual physical feature.
I then added a second version of this line, but with a much thicker stroke and a transparency of 80%. This provides a really subtle, hacked, glow effect.
The abrupt edge of the map at the corners, and the bright imagery at the periphery, distract from the layout.
In the project Layout, you can add a rectangle atop the map, and apply a radial gradient fill (fully opaque black at the outside and fully transparent at center) to burn the edges.
A vignette adds a portrait-like quality to the composition, helping to focus the eye.
Lastly, the brightness of Antarctica, and the visual noise of the graticules converging at center, need to be pushed back. I've added a second vignette overlay, this time reversed, so the center of the radius is darker.
And we can turn the hurricanes back on, for an overall look.
And that's that! Happy mapping. And if you use some of these techniques on your own maps, I'd love to see them -it would make my day. Feel free to hit me at @John_M_Nelson.
Here are a few of the topics covered:
Projection exploration, an image symbology and de-saturation hack, using picture markers for point symbols, using transparency for context layers, and creating vignette effects with radial fills in a layout.
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