Abstract: A high accuracy real-time 3D ultrasonic location system is discussed in this article. The signal received is sampled after passing through a TGC and a logarithmic amplifier. Inside the DSP, a dynamic threshold trace technique is used to improve the accuracy. The result is processed with weighted arithmetic averaging. Tests on a 40kHz 3D location system show that a location accuracy of 1cm is obtained. This system can be made practical after certain improvements.