The LA Times details how a geocoding error in an LAPD online crime mapping app puts a high crime rate just around the corner from City Hall and the Police station. In fact, the spike is the result of failed geocoding.
While the article highlights some key points about the process of geocoding and why the error was not found sooner (the app only shows data back a week, making such spikes less obvious) it missed out on some other points including:
- different apps use different geocoding algorithms
- different apps use different data against which to geocode
- sharing raw data (vs. maps) can help identify such errors
There also this great quote from Paul Zandbergen, a professor of geography at the University of New Mexico who studies the quality of online maps: “Most spatial data are inaccurate.”
My main question is this: Everyblock took the same data feed for its LA maps, and it seems, ended up with same inaccuracies. Is that because they use the same geocoding and data against which to geocode? That’s not clear from the article.
Hat tip to reader Duane for a pointer to the story.
