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Getting Granular: From ZIP Codes to ‘Broadband Fabrics’

Click Here for Main Story: “Broadband Maps Are a Mess, So Now Let’s Focus on Actually Improving Them

The FCC began collecting broadband information by ZIP code. There are 42,000 such codes in the United States. But ZIP codes are not geographic units. A ZIP code assigned to a single large building – as many are – would appear simply as a point on a map.

By contrast, the Census Bureau uses a nesting-doll framework of geographies called the FIPS Code, or the Federal Information Processing Specification. These codes include ID numbers for states, counties, census tracts (66,438 in United States), census block groups (211,267), and census blocks (11,155,486). The census block is the smallest unit of geography the U.S. government recognizes.

Census blocks are bounded by visible features such as roads, streams and railroad tracks and by nonvisible boundaries such as property lines, school districts and city, township and county limits. The average population of a census block is 30, but census blocks aren’t defined by population. They can be quite small in urban and suburban areas but hundreds of square miles in rural and remote areas.

Moreover, these geographical units don’t mesh well with broadband providers’ mapping service areas. Wireline providers use line drawings. The wireless industry employs radio frequency engineers to create propagation maps with polygons that predict coverage areas based on distance from towers. Both mapping techniques create shapefiles that can overlap with census geography and estimate which census blocks are covered.

If a census block is considered “covered” when only one person can get broadband, however, that overcounts broadband availability. One aspect of the State Broadband Initiative was the creation of address-level broadband mapping. But an address-level focus has problems, too. Many addresses are post office boxes or farms with separate structures. USTelecom and rural providers are looking to create what they call a “broadband fabric,” or a geographical map of all structures that might need broadband access. The difference between the broadband fabric and the more limited shapefile approach is that the fabric uses a range of datasets (tax assessor maps, building polygons, parcel boundaries for addresses, and so forth) to determine where broadband needs to go. The shapefile approach, by contrast, reflects the perspective of the carriers, showing the shapes of the areas in which a carrier offers service.

The cable industry group NCTA opposes the broadband fabric approach and instead favors a system in which shapefiles continue to be overlaid against a census block framework.