Block Equivalency to Shapefile Conversion

Block Equivalency Files: A Concise Format for Redistricting Plans

Note: on rare occasions, census blocks will be split in a redistricting plan. In these instances, the Census Bureau requests the block be designated to one district for tabulation purposes.

Let’s say you receive a block equivalency file and you want to view it as a map. As shown above, the file does not include the geographic shape information for each block to render it in GIS or another mapping program. So you will need to find the geometry files for the corresponding blocks, and then join the block equivalency files to them, using the unique block identifier (“BLOCKID” in the sample file shown above) as the key field for the join.

DYK: you can directly upload a Block Equivalency File to DistrictBuilder to view a redistricting plan. Check out this blog for the easy steps:

Once you have the block-level geography file for your location, you can perform the join operation with the block equivalency file. The key field for the join will be the unique block identifier (census FIPS code).

First, make sure Python’s GeoPandas library is installed on your system.

Next, implement the following steps in a Python script to produce a zipped shapefile with each Census block assigned its corresponding district from the block equivalency file.

Now that you have merged the block equivalency file to the block geometry, you can view the districts from the original redistricting plan in GIS or a similar tool. Here is a quick way to inspect your new file in QGIS: Select your layer (this will be the file you created in the previous steps) and select properties to open the layer properties menu.

In this window, select the symbology tab, and at the top of the central menu change the map layer to show categorized data. Working down the menu, change the value to the field showing the unique district identifiers (in our example this was “SLDL” column for the North Carolina House State Legislative Districts), and then we suggest setting the color ramp to random colors unless you have a different visual display in mind. Finally, click classify and you should see all the unique district identifiers values assigned a color. Then click apply to close the properties window and see the district's colors onto the original map.

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