Google does not need to visit you as the collect this data over the Android phones. So basically if there's a single Android user with WiFi enabled (but with GP

Google does not need to visit you as the collect this data over the Android phones. So basically if there's a single Android user with WiFi enabled (but with GPS disabled) they already know your approximate location (due to the GSM cellid). If that happens multiple times they can use triangulation to increase the accuracy of this data. And if there are some Android users with GPS enabled that "see" the WiFi access point, Google can pinpoint the location very very accurate. It's possible to disable this "feature" in the Android settings, but I guess most users don't bother changing this.