Measurement of waves in a small-scale harbour basin using video monitoring technology

Small-scale physical models are used in harbour design to quantify the wave agitation in the harbour basins. It is often necessary to measure waves much smaller than 10 mm in the model for which the noise levels on the signal become significant for traditional resistance and capacitance wave gauges. A new system has been developed consisting of small light-weight floating blocks, called 'Keofloats', which are tracked by a standard video camera. The Keofloat system is insensitive to erratic gauge drift, noise levels are very low and it does not require separate calibration. The accuracy is estimated at 0.2 mm. The Keofloat system has been tested in a flume and compared with capacitance probes. The system has been applied for the measurement of small waves inside a marina. The waves near the marina entrance were measured with both a Keofloat and a capacitance probe. It was concluded from the flume tests that the Keofloats are superior to traditional wave gauges for wave heights less than 5 mm. Keofloats are equivalent to wave gauges for wave heights between 5 mm and 20 mm.