kl 



B. Theory of Analysis 



Selecting the x-y coordinate system in the horizontal with 

 the origin at the instrument's center as in Figure IV-1, the DPG is 

 assumed to faithfully record the water surface displacement "nCx.y.t) 

 at the center, the slopes y\^ at A and C and r]y at B and D. The 

 curvatures ri^x ^^'^ ^yv across the center can be arithmetically 

 approximated by (^Ix*^^) ~ 'rix(C))/Ax and (i1y(B) - T\y(D))/Ay 

 respectively. With the present DPG configuration, it is not possible 

 to arithmetically create the cross curvature term r^^ . An additional 

 measurement would be necessary to define such a term. 



FIGURE IV-1: Coordinate system adopted for DPG analysis. 



