Finding the shortest route from the airport counter to the right gate or getting from detergent to chocolate in the supermarket without detours: With the software from Freiburg-based start-up Telocate, it is possible to navigate indoors with a smartphone with an accuracy of up to ten centimetres. The smartphone emits an inaudible signal in the range above 18 kilohertz, which is received by several receivers distributed throughout the building.