Abstract
GPS (Global Positioning System) is used to determine the position of an outdoor user with a high degree of accuracy, but it works poorly or not at all in indoor locations. Many different techniques have been proposed for indoor positioning, including reference points, such as NFC tags or Bluetooth beacons, radio signal triangulation, and pattern or image recognition [3, 6]. Any of these techniques can be combined with each other or with a dead-reckoning approach, adding user movement data from sensors, in order to arrive at a more precise position estimate [3]. Indoor navigation user interfaces are essentially the same as those used outdoors: maps, turn-by-turn directions, and augmented reality.