Abstract: An acoustic position measurement system and method includes an acoustic transmitter operable to transmit a sound wave into an underground well bore in a target formation. The sound wave is configured to reflect from a boundary formation proximate the target formation. The system includes an acoustic receiver operable to receive a reflected sound wave. The reflected sound wave comprises a reflection of the sound wave from the boundary formation. The system also includes an electronics portion electrically coupled to the acoustic receiver. The electronics portion is operable to process the reflected sound wave and produce, based upon a characteristic of the reflected sound wave, data output indicative of a position of the acoustic position measurement system in the target formation.