That branch of exploration geophysics using refraction and reflection methods of seismographing, employs equipment and methods similar to military sound ranging. Present methods and equipment used in geophysical seismographing show results from developments in the art of sound ranging during the last war. The accuracy obtained in sound ranging is considerably greater than that obtained in refraction shooting where the air wave is used to measure distance. Corrections are applied for direction and velocity of wind, and for temperature. Personnel in the sound ranging unit is organized similar to a geophysical field crew, having motor truck transportation, instrument operators, and record interpreters. However, the geophysical crew is more of a mobile outfit. In any future war, the geophysical personnel, particularly the exploration geophysicist, will be expected to place his specialized training at the disposal of the government.