The geo tag finds its location using GNSS (Global Navigation Satellite System). If it can’t get a GNSS location signal, it can also use MAC addresses from nearby Wi-Fi networks to determine its location. This means you’ll still get an accurate reading even if the device is indoors and can’t connect to GNSS.
If you are interested to learn how will the geo tag work outside the certified areas, please check: Will the Geo tag work outside the certified areas (EU, USA, Canada, Australia, and New Zealand)?
If you are interested to learn how to use geo tag, please check: How is the Geo tag used?