Trilateration is a method used to determine the position of sending units via distance measurement. Such a sending device can, for example, be a smartphone that is carried by a person or a Bluetooth beacon that is attached to a mobile asset. Triangulation additionally takes the angle into account. Since GPS isn’t available in buildings, trilateration and triangulation can be used for indoor positioning and indoor navigation. In order to display objects in 2D, three receivers are necessary, for 3D it’s four receivers.