Figure 10.19 An example of a moored current meter, the RCM 9 produced by Aanderaa Instruments. Two components of horizontal velocity are measured by an acoustic current meter, and the directions are referenced to north using an internal Hall-effect compass. The electronics, data recorder, and battery are in the pressure-resistant housing. Accuracy is ± 0.15cm/s and ± 5°. (Courtesy Aanderaa Instruments)