If you want to use the Global Positioning System (GPS) you need visual contact to several satellites, which is not always given. In outdoor areas it can be interrupted by trees, clouds, tunnels or skyscrapers. Indoors there is hardly a chance to receive GPS signals. But there are multiple possibilities to put into practice an “indoor GPS”. They make use of different techniques, for example Wi-Fi, visual light communication (VLC), smartphone sensors or Bluetooth/beacons. Another advantage if there GPS alternatives is that the floor level can be detected, which GPS can’t.