Performance of Bottom-Mounted Directional Wave Gages

The bottom-mounted directional wave gages (Sea Data models 635-9 and 635-12) have been field and laboratory tested to determine accuracies of the directional information. To obtain high precision directional spectral estimates desirable for inshore use, mounting errors must be minimized and both prevention of fouling and periodic calibration checks of the electromagnetic current sensor in the system are required; in nearshore field use EM sensor gain has been observed to vary by 5% and more between calibrations, not uniformly between axes. With these maintenance procedures, the instruments have proven reliable and accurate.