A method and apparatus for assessing a calibration of a multi-axis ultrasonic scanner, the method comprising: providing a calibration verification tool (100), comprising a plurality of mutually oblique plates (110-140) defining surfaces at predefined angles with respect to one another; providing a digital model of the tool; registering, by the ultrasonic scanner, the tool (100) within the reference frame; controlling the ultrasonic scanner to measure a plate (110-140) to determine a reference signal; measuring each plate (110-140); using the reference signal and the plate measurements, determining an orientation of the ultrasonic scanner when each plate was measured; and, using the determined orientations, verifying whether or not the ultrasonic scanner calibration.