155 



• Window width 



• Order of the potential function 



• Number of water surface nodes 



• Number of samples of the measured record 



• Number of iterations allowed in the optimization 



Some of the criteria that might be used to help define these values are: 



• Non-dimensional depth 



• Ursell number 



• Local curvature of record 



In principle, the LFI method may be extended to additional arrangements of in- 

 struments. While it is straightforward, in theory, to adapt the method to virtually 

 any arrangement of instruments, each different arrangement is likely to present a new 

 set of numerical solution difficulties. One of the sources of this is the use of non- 

 linear optimization. Different optimization problems tend to be unique, and require 

 substantial experience in order to determine the appropriate approach. 



The experience gained in applying the LFI method to a variety of arrangements 

 of instruments helps demonstrate the need for appropriate data. Whether this par- 

 ticular method of analysis is employed, or any other nonlinear technique, the need for 

 accurate data is paramount. The design of a field data collection program inherently 

 includes assumptions as to how the resulting data will be analyzed. Currently used 

 data collection programs are often designed with the assumption that the data will be 

 analyzed with the common methods of linear spectral analysis. As a result the data 

 may not be appropriate for the nonlinear analysis needed to determine the detailed 

 kinematics of a measured wave field. 



Some of the considerations that should be included in the design of a field mea- 

 surement program are: 



