Methods and systems for measuring transducer movement are provided. For example, free-hand scanning for three-dimensional imaging is provided. An optical sensor within the transducer measures motion along the skin surface similar to measuring movement of a personal computer mouse with an optical sensor. Alternatively or additionally, the transducer is tilted at an angle other than perpendicular to the skin surface generally towards or away from the direction in which the transducer is translated. The transducer is then translated while maintaining the angle. Motion to or from the transducer is measured, and a component of the motion measured while the transducer is maintained at an angle is parallel to the direction of translation. The component of motion is angle corrected and used to determine a distance of travel.