-1000 



t 



"1 I I 1 I I \ — I — \ — I — I — I — I — I — I — r 



20 40 60 80 100 120 140 IM 180 



AZIMUTH (degrees) 



Figure E-2 : Artificially generated surface composed of two orthogonal 

 trends, both with spectral slopes of b= -1.5, and a=1.0 in 

 the N-S direction, a=1.2 in the E-W direction. Viewpoint 

 is from the southwest. The variation of a and d parame- 

 ters with azimuth are plotted below. 



206 



