B 



Low -Pass Filter (C) = (D) 



D 



Contoured (D)=(E) 



Figure 4-2 Schematic illustration of the method developed by Davis 

 (1974) for delineating homogeneous roughness provinces 

 within a given spatial waveband. The original signal (A) 

 is band-pass filtered at a pre-selected wave band of inter- 

 est to produce B. The now centered data of B is full -wave 

 rectified by taking the absolute value of all terms to pro- 

 duce C. This output is low-pass filtered (smoothed) to 

 yield the continuous function of D. Finally, this function 

 is contoured at some selected interval (not necessarily 

 linear) to delineate the boundaries of provinces X, Y, and 

 Z in frame E. 



20 



