Your open data visualizations need context; my last crime map lacked any

To have an impact, programmers and journalists need to add context to their data visualizations.  If you just throw stuff up on a map, it may look neat, but it won’t carry much weight and will soon be forgotten.

My regional rail stop crime heat map sucks at telling a story
septa rail stops heatmap
heat map of crime around Septa regional rail stops

Last weekend I hacked together a heat map showing violent crime counts around Septa regional rail stops committed between 2007 and 2013.  It’s not even accurate, since for some reason, it doesn’t show anything around the regional rail stops at the airport.  The point of it was to demonstrate the open source technology that lets your mash up crime locations(or any location) with other locations, and draw inferences.  If you had cancer data and nuclear sites, or brownfield sites, or high tension electric lines, whatever, you could apply the same technique.

I didn’t think the map would get much play, but it did, since it didn’t do much.  Philebrity posted about it, but was tongue in cheek about it: “There’s no indication how many of the crimes were against SEPTA passengers, what time of day they occurred, or how many were of which crime. But hey, now you know.”  In other words, “this doesn’t say much but there are red parts of Philadelphia and we have post quotas”.  They were in on the joke.  But there was a commentor who called my map on it’s lack of context:

This is not a helpful map because it doesn’t account for population density or passenger volume or some other proxy to explain why there is obviously going to be more crime when there is a very high density of people in a particular area. I think a quick glance tells you that you are probably safer at 17th and Market than you are at 21st and Allegheny but this map doesn’t reflect that at all, in fact it tells you the opposite. This map should be dealing in the relative RATES of crime, rather than total number of crimes.

That’s dead on.  Of course center city rail locations have more crime, there’s more people there.  And just because the heat map shows red, doesn’t mean you’re in more danger of being a victim of violent crime.  I’m currently searching for ways to heat map the rates of crime to add context to crime near transit stops.

Philly crime visualizations so far

It’s been a year since the city has released it’s crime data to civic hackers.  And though there has been a a few very stylish visualizations, enough for the Atlantic Cities Blog to note, I’m not seeing much context associated with them.  There are 15 homicides in the triangle, so?  There looks like there’s more murders in Frankford than Mayfair, so?

There is a spot on quote in the Technically Philly post announcing the crime data release:

“…in private conversations with IT leads within the city and representatives elsewhere, there is real political concern about the impact of near real-time, automated crime mapping. Wouldn’t that make some neighborhoods look bad and create winners and losers, one council member once asked …”

I really thought that was going to happen.  I was picturing a new age of digital redlining where the middle class would look at heat maps and stay away from those areas.  That never happened.  The reason, I think, is that the visualizations lacked context.

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