I've talked about 3D mapping here before, and why I like it, so I thought it was about time for another one. Since the US presidential elections have just taken place I thought I'd look at some of the data and make some maps. I'll post some more when I have time but for now I thought this 3D map showing the ratio of Obama to Romney voters at the county level was pretty interesting, not least because it identifies an interesting high point in South Dakota.
Click here for a full screen version
South Dakota is a Republican stronghold but Shannon County is the exact opposite. In both 2004 and 2008 it had the highest Democratic voting percentage in the United States (over 85% both times) and in 2012 more than 93% voted for Obama. This might not come as a surprise when you discover that Shannon County is located entirely within the Pine Ridge Indian Reservation and that out of around 8,700 registered voters, 6,500 are registered Democrats.
One advantage of using a 3D choropleth is that you can often differentiate between places within the same class in a way that is impossible with a normal 2D choropleth. It usually makes it very easy to see places that stand about - such as Shannon County - and it is a powerful way to visualise this kind of data. There are down-sides too (visual occlusion being one of them) but the continental United States is a nice shape with nicely divided counties, so it works well there.
Beyond Shannon County, the Obama strongholds with real weight in terms of population are DC and the Bronx. In both cases Obama voters outnumbered Romney voters by more than 10 to 1 - 222,332 to 17,337 in the case of DC and 264,568 to 24,430 in the Bronx.
More on this kind of thing coming in the near future...