Google says it is changing the way that it maps people s wireless access points in its efforts to provide accurate location information. The company said it is now encouraging users to add a _nomap extension to the SSID of their access points if they don t want Google to map them. Google and other companies use the data that access point broadcast to build a database of the access points location. It then uses that data to pinpoint users locations when they re using location-based services such as Google Maps.
Source: https://threatpost.com/google-allow-users-opt-out-wifi-location-mapping-system-111511/75895/