Figure 2.40. Examples of two types of ADCPs and representation of the geometry of their beams. The one to the left has a classic “Janus” configuration, in order to measure vertical three-dimensional current profiles (speeds according to X, Y and Z at different depths). The one to the right has a special configuration that enables the measurement of two dimensional currents in a horizontal plane (speeds according to axes X and Y). The two devices enable study of the swell by measuring wave-induced orbital speeds (Courtesy of Teledyne R.D. Instruments)