#IronViz Recap Part 1: How to Build Trapezium Tile Maps

Jul 6, 2018

Klaus Schulte

Some of you may have seen the #IronVizEurope grand final, where trapezium tile maps (Neil Richards labeled them this way and I quite liked it) for Europe played a significant part in my winning viz on the Big Mac Index.

I had seen a trapezium map only once before in this cool viz by Heidi Kalbe:

While Heidi uses trapezium shapes in a grid, I wanted to use polygon data due to the special #IronViz situation, having no time to figure out the right size of the shapes to make the distances between the shapes look really accurate. With a polygon map I would be able to just bring in the data, set a border and go for it.

To build a polygon map there are many blog posts and tutorials around explaining how to do it. I personally watched this tutorial from the Tableau website. Basically you just need X,Y-coordinates and a point order to tell Tableau in which order to connect these coordinates.

To build my map I first sketched it in Powerpoint:

Looks nice.

Then I needed just a little bit of geometry. I built my trapezes out of three equilateral triangles what allowed me to calculate the coordinates of my trapezes in excel very easily:

- An equilateral triangle has all sides the same length. The altitude of the triangle can be calculated as shown below.

- Taking three of them looks like this…

- …resulting in these exemplary coordinates:

To get all the coordinates I just lay a grid on top of my sketch. So I was able to calculate all the coordinates for any given l.

The rest is just bringing the data to Tableau and creating the viz:

After some formatting it looked like this in my viz (Interactive version on Tableau Public):

Feel free to use my Europe trapezium tile map to create own ones and bring it to the next level! You can find the data here: Data Europe Trapezium Tile Map.

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