Sodar (sonic detection and ranging) systems are used to remotely measure the vertical turbulence structure and the wind profile of the lower layer of the atmosphere. Sodar systems are like radar (radio detection and ranging) systems except that sound waves rather than radio waves are used for detection. Other names used for sodar systems include sounder, echosounder and acoustic radar. A more familiar related term may be sonar, which stands for sound navigation ranging. Sonar systems detect the presence and location of objects submerged in water (e.g., submarines) by means of sonic waves reflected back to the source. Sodar systems are similar except the medium is air instead of water and reflection is due to the scattering of sound by atmospheric turbulence. Most sodar systems operate by issuing an acoustic pulse and then listen for the return signal for a short period of time.