Remember the farm in Kansas that, thanks to an error in MaxMind’s geolocation database, became the default physical location for any IP address in the United States that couldn’t be resolved? It’s happened again, this time to a couple in Pretoria, South Africa, who received online and physical threats and visits from the police because IP addresses that were from Pretoria, but whose precise location couldn’t be resolved any further, defaulted to their front yard. Kashmir Hill, who covered the Kansas incident, has the story for Gizmodo. It’s a fascinating long read that burrows into the sources of geolocation data and the problematic ways in which it’s used.

In this case the problem was traced to the National Geospatial-Intelligence Agency, which assigned the lat/long coordinates for Pretoria to this family’s front yard. The end result: one home becomes the location for one million IP addresses in Pretoria. (The NGA has since changed it.)

The problem here is twofold. First, a failure to account for accuracy radius: a city or a country is represented by a single, precise point at its centre. That’s a real problem when the data point being geotagged can’t be more specific than “Pretoria” or “United States,” because the geotagging is made artificially precise: it’s not “somewhere in Pretoria,” it’s this specific address. Second is the misuse of IP location data. It’s one thing to use a web visitor’s IP address to serve them local ads or to enforce geographical restrictions on content, quite another to use that data for official or vigilante justice. The data, Hill points out, isn’t good enough for that. [MetaFilter]

Previously: A Geolocation Glitch Creates a ‘Technological Horror Story’.