Whenever, users launch Google map on Android, it displays their current location in most cases.
Users often wonder that how Google Maps accurately estimates their location even if GPS is disabled.
Google and others like Apple build a Database which links WLAN BSSIDs to a geographic location. A BSSID is like the MAC Address of a access point that gets transmitted by that access point. It is therefore public viewable if the BSSID broadcast is enabled, which is the default for most access points. BSSID operates on a lower layer as the IP layer stack, user don't even have to be connected to an access point to receive these broadcasts. So, it submits the basic location of user to the Google maps.
BSSID(Basic service set identification) is generated by combining the 24 bit Organization Unique Identifier and the manufacturer's assigned 24-bit identifier.
Also, when user browse Google Maps or Navigation with enabled GPS and WiFi and if device is able to get a good GPS, the current visible WLAN networks and current location are uploaded to Google to build and update the database. This technique is sometimes called crowdsourcing and every Android device acts therefore as data collector.
Previously, they used mainly cell towers and locate towers which provide user's cellphone's calling/receiving connection and are close to user. They use respective distances from the towers to you to calculate your exact location. In this way, location of cellphones was calculated before the popularity of GPS and WiFi technology.
So, these methods are often used to get precise location of the user.