theoretically possible for the solution to converge to a subsidiary min- 

 imuffl and therefore yield a poor model. However, the selection of the 

 initial a^ and b^ by a regression in log-log space makes convergence on 

 subsidiary maxima unlikely. An ASCII FORTRAN 77 subroutine for perform- 

 ing this algorithm is presented in ^pendix A. 3. 



In practice, the regression models for the amplitude spectra (and 

 final roughness model) are formulated interactively with a graphic dis- 

 play terminal. The operator can interactively edit the ba thyme trie pro- 

 file under examination as well as control the frequency limits included 

 in the regression analysis. This allows the software to delete white- 

 noise levels, interpolation effects, and other contaminating factors 

 from the analysis. The interactive control also allows the operator to 

 detect visually spectra composed of two power law segments, and to fit 

 each segment Individually. This Interactive software is included in the 

 amplitude spectrum generating software listed in Appendix D. 



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