Illustrates the characteristics of a surface in which two signals of 

 identical spectral slope (b = -1.5) and Intercept (a = 1.0) were com- 

 bined in orthogonal directions. Arbitrarily assuming a viewpoint from 

 the southwest for all examples, the input signals represent pure signals 

 in the east-west and north-south orientations. The resulting surface 

 shows a clear northwest-southeast trend. Another realization might 

 yield a northeast-southwest trend. With only a knowledge of the result- 

 ing surface, an investigator might infer a single process acting at 45° 

 or 135° azimuth. The trend actually results from the vector sura of two 

 orthogonal processes. 



The distribution of spectral parameters with azimuth clearly 

 reflects the departure of this surface from a one process model. The 

 spectral slope parameter (b) does show the designated value of -1.5 at 

 azimuths of 0°, 90° and 180°, as it must. The corresponding intercept 

 (a) parameters <ij.3o correspond to the input value of 1.0, indicating 

 that these profiles represent uncontaminated samples of the input sig- 

 nals. At intermediate azimuths, however, both parameters are consis- 

 tently higher than those of the input signal. Whereas in the simple 

 model of Chapter 6 the slope (b) parameter remains constant with azi- 

 muth, the same parameter shows two clear maxima in the range 0° to 180°. 

 The intercept (a) parameter also shows two maxima, rather than the 

 single maximum of the corrugated surface model. Figure E-2 presents a 

 similar surface in which the Intercept (a) parameter in the east-west 

 direction has been increased to 1.2. The variation of spectral param- 

 eters with azimuth is also very similar to that shown in Figure E-1, 

 however the variation of both a and b is amplified. 



205 



