FatFonts are a great new concept by Miguel Nacenta, Uta Hinrichs, and Sheelagh Carpendale for presenting numerical data in an easy to understand way, but while leaving the numbers readable.
The idea is that numbers with a large value appear fatter and darker than numbers with a small value which appear thinner and lighter. This means that if you want to plot something like a height map, where each pixel has a value equal to its height, you can just write out the numbers and they build the image for you. The really clever bit is that if you have a multiple digit number, like 8242, the 8 (8 thousand) appears biggest, the first 2 (2 hundred) appears a bit smaller, the 4 (4 tens) appears even smaller and the last 2 (2 units) appears tiny.
It is always easier to explain concepts like this with a picture, so here is some data:
It is hard to look at this and see the shape of the data, but if you use a FatFonts presentation (this font is called Miguta):
You can now actually see the shape of the data, where the bigger numbers are and where the smaller numbers are. This example is of the number 8242 I mentioned above:
The 8 is biggest (8 thousands), the 2 is nested inside it (2 hundreds), then the 4 (4 tens) and finally the last 2 (2 units) is too small to see.
I have coded a couple of fonts (Miguta and 7 Segments) for Miguel Nacenta to make this technique really easy to use. Check out the FatFonts 'how to use' guide for more information.
And here is an example of my FatFonts 7 Segments design in action; http://studiolakmoes.nl/datavisualisatie-met-fat-fonts/
Inkscape: Managing Miguel's glyph designs
Fontforge: Font preparation and contextual alternates coding