Show Me the Data

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!”

(via LAObserved)

Technorati Tags: , , , ,


  1. This is actually very cool. I have a very close friend who is the director of a homeless outreach/shelter program in a suburb of Atlanta. Over the years, we have often discussed this very notion that during cold weather (more so than any other type of incliment weather) people who have a place to go move off of the streets into those places.

    I think this new technology has many implications, but for the purpose of tracking trends in the number of homeless people in a community that it has some great potential of giving hard data to support the anecdotal knowledge of those who serve this population. For the savvy nonprofit, the data can be turned into a wonderful business case for increased funding/resources during certain months of the year.

    Now for many, the challenge comes in garnering the assistance of the law enforcement in the area or finding the folk to conduct the surveys.

  2. Carol,
    You are absolutely right. The key for others is in knowing how to use this kind of data most effectively in their programs, and in figuring out how to collect that data efficiently.

  3. Nedra, are you familiar with the National Cancer Institute’s Consumer Health Profiles? They are maps of clusters in need of various cancer screenings and outreach by neighborhood and supplemented with information on the type of consumers the members of these “clusters” were. The clusters’ composition were based on results from a number of health surveys such as pulse and consumer surveys. That way the outreach specialist could truly target the intended audience where they are and where they may be absorbing messages most. I used them a great deal when I worked with the NCI Cancer Information Service. They were an excellent tool to use in cancer outrreach and prevention efforts.

  4. Shari,

    Thanks for the information. I did not know about the NCI’s profiles. They sound like an incredibly helpful tool.

  5. hello from Paris France,

    Excuse my poor English…

    Excelent projet!
    An other one can be helpfull.
    Mapping the rich people to help the homless from L.A to know the best place where they can beg.

    virtuellement yours


  6. I have been using a GIS since 1994 to map the location of poverty and poorly performing schools in Chicago, as well as the locations of non-school tutor/mentor programs. I use this information in a marketing campaign intended to draw a better distribution of volunteers and donors to all neighborhoods where tutor/mentor programs are needed.

    At I write about this and show links to others who are also demonstrating uses of GIS.

    We’re doing this with volunteers, so are always looking for partners.

    Dan Bassill
    Tutor/Ment or Connection

  7. Virtual,
    I think the homeless have found the sweet spot in Santa Monica — lots of affluent residents and tourists coupled with a city government that does not do much to discourage their presence.

    Thanks for sharing what your program has been doing. It’s a great example of using GIS to make strategic decisions.

Submit a Comment