From GizMag: While GPS tracking tends to be ineffective inside buildings, alternative indoor positioning solutions require the presence of Wi-Fi network access points or other beacons … or at least, that was the case before a Finnish start-up called IndoorAtlas stepped onto the scene. Its software uses your phone’s built-in compass and measures the anomalies in the Earth’s magnetic field to pinpoint your location in a building with the accuracy ranging from 0.1 meter to 2 meters (3.93 inches to 6.56 feet). If spiny lobsters can do it, so can we, the logic goes.