Google lets Wi-Fi network owners opt out of mapping

Simply adding "_nomap" to the name you've given your domestic WiFi network will prevent Google Maps-equipped cellphones using your home as a position fix, Google announced last night. The idea is to allow people the chance to opt out of helping provide Google's commercial positioning service - even though doing so is likely to degrade its accuracy.

Google announced the opt-out option on its blog today in a further move to assuage the criticism it faced over its infamous Wi-Fi data sniffing operation carried out in 2010. When Google's Street View cars photographed our streets and used laser radar to get the shapes of buildings right in Google Earth, it also sniffed the air for two key ID numbers on the Wi-Fi networks at each property: the router's hardwired Media Access Control (MAC) address and the Service Set Identifier (SSID) - the name you've given your network. However, lax controls on the MAC/SSID sniffing software resulted in Google also acquiring personal data, such as snippets of our emails and web requests - leaving it censured by data protection authorities.

Why use Wi-Fi data for positioning? When phones can't get a GPS satellite fix in a built-up area, triangulating signals from either cellphone antennas and/or Wi-Fi routers can provide a reasonably accurate position fix. So, Google and rival providers like Skyhook look for and store our MAC and SSID data on their location servers.

However, pressure groups like Privacy International complain that databases of Wi-Fi IDs were surreptitiously compiled and that people should be able to opt out. This is what Google has provided today. But while adding _nomap to your SSID will prevent passing Google devices using your network, it won't stop its rivals using it. But Google hopes the opt-out format will be adopted by its rivals, too.