US Patent 7417923 Method and apparatus for performing an ultrasonic survey

An ultrasonic surveying method includes a network of transceivers adjacent the item to be surveyed to establish a reference plane and locating an array of pingers on the object to be surveyed to establish a survey plane, establishing by ranging from the pingers to the network the location of the survey plane, detecting relative motion between the network and the pingers and correcting survey measurements for the detected motion.