Directional Wave, Currents and Environmental Monitoring from Navigation and Hydrography Buoys: An Introduction to Motus

Aanderaa's Directional Wave Sensor, Motus (movement in Latin) is a compact, low power accelerometer-based sensor designed to accurately measure multi-spectrum directional waves from standard hydrography and navigation buoys. An inbuilt feature is its flexibility as it can be used on variety of buoy types and does not require a center of gravity placement. An external compass can also be integrated if magnetic disturbances are present near the sensor. To date, two buoys, Xylem's YSI EMM 2.0 and Tideland SB-138P, have been tested with Motus. Here we present field data that demonstrate excellent agreements between wave measurements from Motus sensors fitted on the two buoys, and a dedicated circular wave measurement buoy (Datawell Waverider MKIII) The Xylem buoys were also equipped with Aanderaa current sensors to demonstrate the multi-parameter features and capabilities of the buoy platforms. The maximum recorded average wave heights were above 7 m. Since the DCPS can run in both narrowband and broadband modes, we also demonstrated that measuring currents in broadband mode from a moving platform results in noisy and ultimately unusable current velocity data.