1. Directional Wave Observations 1) Da Basics 2) Remote Sensing v. In Situ : It’s all good. 3) Estimating directional wave properties. 4) Measurement accuracy and user needs. 5) A Recipe for instrument evaluation.

2. z x y w u v The Big 3 X, Y, Z The Basics: Estimating the Motion of a Sea Surface Particle Pressure Sensors Accelerometers Tilt sensors Angular Rate Sensors Acoustic Sensors Radar Lidar dz/dx, dz/dy z

3. In-Situ and Remotely Sensed Waves Method O(cm) X,Y,Z Accuracy Spatial Coverage Time Coverage In situ SAR,LIDAR HF, X-Band Radar In situ and remote sensing systems are complimentary, NOT redundant.

5. The Big 3: X, Y, Z  Time Series Analysis  The Fab 5: S(f),a1(f),b1(f),a2(f),b2(f) !! S

6. - mean direction - directional spread - skewness - kurtosis or, in NDBC format - first-moment mean direction (θ1) - first-moment spread parameter (r1) - second-moment mean direction (θ2) - second-moment spread parameter (r2) a1,b1,a2,b2 1 b1 a1 r1 θ1

7. S(f,θ)=S(f)[a1·cos(θ)+b1·sin(θ) +a2·cos(2θ) +b2·sin(2θ) +a3·cos(3θ)+b3·sin(3θ)+ a4·cos(4θ)+b4·sin(4θ)+………………infinity and beyond] Wave Direction θ Wave Energy Density The Directional Spectrum

9. Data Users & Measurement Accuracy Dominant Wave Users θ S(f), 1 @ f-peaks Wave Component Users Fab 5 Generally tolerant of errors. Need a wave component approach to evaluating instrument performance.

18. Conclusion Let’s talk about the Fab 5 This is the current state-of-the-art. This is the bar modern wave instruments should have to clear. This is the standard emerging technologies should try and achieve before pursuing the Fab 7, the Fab 9….