ANDERSON: BOTTOM PROPERTIES FOR LONG-RANGE PROPAGATION PREDICTION 



• Models of bottom interaction presently used in propaga- 

 tion models 



• Models that allow the inclusion of bottom effects: bottom- 

 loss models and geoacoustic models. 



• The order of magnitude of observed and predicted bottom 

 loss values 



• Measurement techniques and presently available data for 

 acoustical and other physical properties of the bottom 



• The sensitivity of bottom loss to variations of the input 

 sediment parameters 



• The sensitivity of propagation predictions to variations 

 in the bottom information. 



Unresolved issues concerning bottom properties for long-range 

 propagation include the following questions: 



• What is the sensitivity of predicted long-range, low- 

 frequency propagation loss to variations in the sediment, 

 either bottom loss or physical parameters? 



• What is the sensitivity of bottom loss to sediment param- 

 eter variation? 



• To what depth and in what detail do we need sediment 

 information to predict bottom loss? 



• What information do we now have and what techniques need 

 further measurement? 



Two general techniques treat mathematical propagation problems. 

 These are, of course, ray theory and wave theory. Each technique may 

 treat the bottom as a reflecting surface or as part of the propagation 

 path. 



For example, in the ray -theory models we identify eigenrays by 

 searching through ray families until we find two that bracket a 



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