You might have noticed but I'm a reasonably big Twitter user. Actually, I should be more precise. I'm a reasonably big Twitter API user ... I tend to use Tweetdeck on my mobile devices and on my laptop. I very rarely use Twitter on the web, and so I've only just noticed how Twitter are handling the display of geotagged Tweets. Take a look below and you'll see that on the accompanying map that they're rolling up from the point of the geocode to the nearest administrative geographic entity and highlighting this in a rather fetching shade of transparent red.

For Tweets at home, the geotag rolls up to the London Borough of Richmond-upon-Thames, although I had to check this as I was pretty sure the Borough didn't have that shape; I was wrong on that count.

In Berlin, the geotag rolls up to the Bezirke or borough, as shown in the example below, Tweeted from Berlin's Tegel airport. The vector of Reinickendorf can clearly be seen.

But sometimes the vector data just isn't there. The final example, Tweeted from Hampshire merely shows what I assume is the minimum bounding rectangle for the county.

As a final note, this feature doesn't appear in the "new" version of Twitters web site, where only the name of the geotag's location is displayed; if you want to see this in action yourself, you'll have to switch off the "new" version's preview and revert to the older user interface.