Strapped-down accelerometer effects on NDBO wave measurements

Equations for wave displacement measurements by buoys equipped with strapped-down accelerometers are derived and used for computer simulations of wave measurements for a variety of sea states. Use of strapped-down accelerometers causes measured acceleration to be a sea state dependent time varying combination of buoy vertical acceleration, buoy horizontal acceleration, and acceleration due to gravity. As a result of the nonlinear equations that describe strapped-down accelerometer measurements, measured wave spectra have excess low frequency energy. Buoy responses to waves are considered to quantify error levels of operational NOAA Data Buoy Office buoys with strapped-down accelerometers. Simulations of several thousand buoy measured wave records and processing of these records in a manner similar to operational processing indicate that strapped-down accelerometers introduce significant wave height errors that are generally less than 5%, but that effects on low frequency swell measurements are at times substantial.