Abstract: The probe tip of a scanning probe microscope is scanned either along an X- or Y-direction of the apparatus, or along a scan line forming an acute angle with both the X- and Y-directions. During scanning, an excitation vibration is applied in the Z-direction, perpendicular to the surface of the sample being scanned. In a first mode of operation, a dithering vibration is applied to the probe tip, along the scan line. In a second mode of operation, the probe tip is dithered in a circular motion, which is used to identify the direction in which a wall extends along the sample surface. Alternately, in a third mode of operation, the probe tip is dithered in X- and Y-directions at differing vibrational frequencies to identify this direction of a wall. When this direction is identified, the probe proceeds straight up or down the wall to obtain an accurate profile thereof.