Using LDV, laser pulses emitted from a sensor are reflected from microscopic particulates naturally entrained in the air. These particulates are comprised of microscopic desert sand, volcanic ash, and cosmic dust that filter through the Earth’s atmosphere from space and other atmospheric scatterers. The effect of a laser scattering from these types of particulates can be observed by shining a laser pointer in the air at night or at any laser light show; it is, in fact, the only reason that the laser can be seen. Since the scatterers move with respect to the sensor (either the sensor moving through the air on an aircraft or the wind moving past the ground-based sensor), the color (wavelength) of the laser light that returns to the source is shifted slightly.  This shift in color, known as a Doppler Shift, of the laser light is a measure of the speed at which the air moves relative to the sensor. The sensor measures this Doppler Shift, directly reading the airspeed or wind speed. A complete three-dimensional picture of the aircraft movement through the air or the wind around the runway is created by measuring this shift in at least three non-collinear directions. 

While Laser Doppler Velocimetry is renowned for its effectiveness in measuring atmospheric winds, its applications extend far beyond. It can also be used to measure the speed and direction of solid objects like cars, tanks, and even determine the relative movement of an aircraft over the ground.