Volume Three Appendix 12 4. Direct measurement of wave properties 4.1 Wave properties used to calculate Wave Energy from a directly measured Wave Record must be determined according to the following conditions and assumptions: (a) Measurements must be made by, or under the supervision of, a competent professional experienced in the measurement of waves using an appropriate, calibrated wave measurement instrument and accepted data analysis methodologies. (b) Measurements must be made at any of the sites identified in Table 1 above and must be undertaken only in conditions when those sites are substantially clear of kelp and other obstacles. (c) Measurements must be made in depths of water of between 1 and 5 metres. In order to calculate Wave Energy, the wave properties determined from the Wave Record at the point of measurement must be transformed to a standard depth of 3 metres using the following methodology or assumptions: (i) Shoaling and refraction analysis to calculate a transformed wave height must be based on Snell's law assuming that the seabed contours are parallel with the direction of travel of the ship, and that the angle between the wave crests of the waves generated by the ship in deep water and the seabed contours is 55°. (ii) A local water depth of D + ½H, where D is the average water depth and H is the measured wave height applicable to the Wave Record, must be adopted in the shoaling and refraction analysis for the purpose of calculating group wave celerity and wave length. (iii) The effects of bottom friction, viscous effects and turbulence must be ignored. (iv) Wave period must be unadjusted from that determined at the point of measurement. (d) Measurements must be made only under calm conditions which shall be deemed to exist where the Significant Wave Height related to wind and other disturbances (other than the ship under evaluation) at the measurement site does not exceed 0.05 metres based on a Wave Record recorded for a duration of not less than 5 minutes immediately prior to recording ship Wave Energy. (e) For the purposes of calculating wave characteristics under this Plan, the density of water must be taken as 1025 kilograms per cubic metre, the gravitational acceleration must be taken as 9.806 metres per second squared, and any other physical parameters required must be those applicable at a temperature of 15°C. App 12 – 3