As mobile and wearable technology has evolved, an increasing need for indoor positioning has arisen. In particular, the use of ultrasonics provides a cheap way to fulfil this need. However, current ultrasonic location systems have to be calibrated manually by providing information about the exact positions of the transmitters used. Where systems are to be deployed over a large number of rooms in a building, or in rooms where the transmitters are out of easy reach, manual calibration is particularly time consuming.
In this paper, we describe an autocalibration algorithm to compute the position of ultrasonic transmitters using sets of distance readings. This eases the calibration of ultrasonic location systems at the initial setup stage, and eliminates the possibility of errors in taking manual measurements. We show that an autocalibrated system can produce accurate location results.