Where do Google and Twitter source political boundaries of cities, regions and states?

Question

I have recently noticed the nice dashes that Google Places puts around cities, regions, states etc. I've been hunting around in the Google Maps API and the Google Places API trying to find out how to access the information thus displayed, without success.

I've discovered that Twitter has a nice API for this and I would be tempted to use that instead of Google's, but I worry that the lines that Google draw and the lines that Twitter draw may not correspond.

Is it safe to assume that both companies are using the same data? If not, where do I find the appropriate API information for the Google implementation?

Alternatively, where do I find the geodata they're both using?

PLEASE NOTE I'm asking about this in the context of Australian geodata. Do Google and Twitter use the same or different resources?

Answer 1

Most info is at the Census Bureau website. The state and county boundaries are in the section about TIGER files.

Drilling further, the Census Bureau subdivides counties into census tracts, and tracts in census blockgroups, which in turn contain a set of blocks like the one you live in. While states and counties overlap the administrative divisions we know, tracts and blockgroups do not.

There are boundaries defined by different government agencies which are not hierarchically connected to a census entity but are instead in a parallel taxonomy. This is the case of the Metropolitan and Micropolitan Statistical Areas defined for budgeting purposes.

Google is probably (but I'm not sure) displaying Urban Areas, which is another taxonomy grouped on a population-density criteria. An Urban Area can exist in more than one census tract or even more than one county at the same time. There are relation files that map the entities to other entity families.

Finally, there are some "entities" that arent geometrical but popular culture considers them to be. This is the case of USPS Zipcodes, that do not amount for a geometry and have a very loose mapping to real geographical entities.

For any attempt to draw border lines in an application, states and counties are 100% safe to draw. For smaller entities, I'd reccomend sticking to census tracts and census blockgroup boundaries. The other entities have blurry edges, evolving definitions, contradicting boundaries and should be taken as a mere reference.