Unlike PIV, PDV requires only a single image of the flow field. This image may taken over a long period (relative to characteristics times scales within the flow) to produce time-averaged images or alternatively using a single laser pulse (approximately 10ns) to obtain a measurement of instantaneous flow velocities. The duration of a single laser pulse is at least an order of magnitude shorter than pulse separations used within PIV. This feature of PDV enables improved resolution of sharp velocity discontinuities such as shock waves.