Downtown Los Angeles has the largest homeless population in the US. But until recently, the data on the problem has been spotty. Starting in November 2006, the Los Angeles Police Department (LAPD) has been surveying the streets of Downtown every two weeks to count the number of homeless people, their exact locations and some basic demographics. All this data ends up on an Excel spreadsheet. But what could they do with this raw data? Just looking at the numbers is almost meaningless, since there are so many data points to compare.
Enter Cartifact, a custom mapping firm based in Downtown LA. They offered to work with the LAPD to help them visualize the information in a meaningful way and to see changes over time. Together the LAPD and Cartifact have created the Downtown Los Angeles Homeless Map, which takes the information from the biweekly Excel spreadsheet and converts it into a GIS-based heatmap superimposed on a street map of Downtown that shows the density and location of homeless people on each day of data collection. The individual maps are animated together to show the changes between each two-week period.
Eric Richardson, who writes blogdowntown, is also the lead developer for Cartifact. He notes on his blog how the most recent data provided some immediate insights into what is happening with the homeless population:
Interesting to note, though, is the way in which temperature affects the number of people on the street. It’s cold outside, and has been for several days now. The count for January 15th (Monday) was down 271 people from January 2nd. It got cold and the people who could find somewhere to go did so.
And in the comments he explains why these maps are helpful:
But also this sort of visualization is vital because it tells us what trends are occurring over time. Since enforcement of Safer Cities began there has been a definite spread of homeless to areas outside of Skid Row, particularly into the Toy District, the Fashion District and into South Park. Anecdotally we see this every day, but visualizing hard data allows us to say it for certain. That sort of knowledge is important for planning strategy.
This type of mapping could be used very effectively as a basis for understanding many health and social problems in a particular geographic area. Imagine using this to map the spread of an infectious epidemic – you could easily see what direction it was moving in, what types of neighborhoods it hit the hardest, what the boundaries of a quarantine area might need to be. You could look at areas with high exercise density (where people running or walking for exercise tend to be found) and make sure there are sidewalks and crosswalks on those streets. Map out gang-related incidents to see where to concentrate your violence prevention billboards or locate your program’s youth drop-in center.
I’m sure some form of mapping is occurring in many programs. The advantage of this model is that the heatmap format conveys a lot of information in a quick glance, and that it is easy to visualize changes over time. As Jerry Maguire might have said, had he been a social marketer rather than a sports agent, “Show me the data!”