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Mapping Los Angeles' 2010 Census Numbers

By Eric Richardson
Published: Sunday, March 13, 2011, at 04:30PM
2010 Census Maps blogdowntown

Maps showing Downtown population change, Downtown density, population change by City Council district, County population change and County density are available from blogdowntown's Census Maps page.

How has Los Angeles County changed in the last ten years? The detailed data released by the U.S. Census Bureau on Tuesday gives the government's official view of California, but many of the interesting statistics are buried inside a sea of numbers.

Building off the work started on Wednesday with our Downtown population numbers, I've put together a collection of maps showing a few of the aspects the numbers reveal about L.A. County, our City Council boundaries and Downtown.

Click here to see maps, including Downtown population change, Downtown density, City Council population change, County population change and County density. All maps use SVG, which will not work in Internet Explorer.

Making the Maps

While geographic data is traditionally the world of expensive ArcGIS installations, the creation of these maps involved only free, open-source software.

Data downloaded from American FactFinder and Census Redistricting Data.

Census tracts change every ten years, so to map 2000 tracts to 2010 tracts you need the 2010 Block Relationship Files, particularly the 2000 tabulation block to 2010 tabulation block file.

From there, I wrote a Ruby script to take 2000 block population data and the 2000 to 2010 block relationship mapping and use them to create 2000 population for each 2010 block. A similar script mapped 2000 population to 2010 tracts.

Another script parsed through the raw redistricting data file to extract 2010 population by block for Los Angeles County.

For City Council numbers, I took shapefiles of the district boundaries and the 2010 census blocks and imported them into PostGIS. A script then ran a query to match census blocks to council districts, pulling in the previously-created population file to output both 2000 and 2010 populations for each district.

I used QGIS to visualize the work I was doing, attach the computed numbers to the appropriate shape files and export the GeoJSON files that I would need for mapping.

Maps are created using the Polymaps Javascript library, pulling underlying map tiles from Cloudmade. The little bar graphs are made with Protovis. I wrote a little Javascript library to tie it all together and reduce code duplication between the different maps.

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