8. Smaacy and Coadasloas 



A method has been developed to allow a valid stochastic descrlptioa 

 of sea-floor relief to be generated in a. relatively simple statistical 

 model. The fundamental statistic used is the amplitude spectrum of spa- 

 tial frequency, which is both elementary enough to be generated opera- 

 tionally from existing digital bathymetric data bases, and general 

 enough to be applied to a variety of engineering applications and scien- 

 tific problems. The model allows relatively large areas of the world 

 sea floor to be described by as few as two model parameters for simple 

 isotropic surfaces. The difficulties of producing a stationary statis- 

 tic in a non-stationary environment are minimized with the use of a spa- 

 tial domain provincing technique. The model also accounts for the 

 directional dependence of anisotropic surfaces. The results of one sim- 

 ple experiment indicate that the model may be extrapolated with high 

 fidelity to frequencies beyond the resolving capability of surface ship 

 sonar systems. This stochastic model when combined with lower frequency 

 deterministic models, such as the gridded bathymetric models developed 

 by NAVOCEANO, allows a complete description of the sea-floor relief. 



There are numerous avenues available to improve the model. The use 

 of ensembles of either data or derived statistics allows the estimation 

 errors of the model to be reduced substantially. The availability of 

 multibeam sonar systems makes this improvement possible immediately. 

 The ensembling of the statistics from the sixteen beams of the SEABEAH 

 system would reduce the estimation error to one quarter the results from 

 a single beam. Data derived from very narrow beam sonars allow a higher 

 rate of sampling, and therefore a wider frequency band, to be available 



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