Current technologies include GPS, IR, ultra-sound, RFID, Bluetooth, UWB, magnetic technology, and WiFi. GPS is the most widely-used technology for location and positioning, but is very inaccurate in indoor environments due to signal loss
Zhai 2015.
Information provided by one or more wireless sensing technologies is used to locate and provide location information. Techniques include triangulation, fingerprinting, proximity, and vision analysis
Deepesh 2016.