Figure 1.1: Segment of record considered for global approximations 



conditions, and thus do not take into account the interactions between the individual 



1.2 Methods for the Interpretation of 

 Irregular Wave Records 



Methods used for the interpretation of irregular wave records fall into two general 

 categories: global and local approximations. Global methods seek a solution that 

 matches an entire measured record, or a single complete measured wave, from trough 

 to following trough, or zero crossing to zero crossing (Fig. 1.1). These methods apply 

 the same frequency and wave number (or set of frequencies and wave numbers) for 

 all z (vertical variation) and t (time). 



Local methods, on the other hand, seek an approximation to each small local 

 segment of a measured wave. In these methods, the frequency and wave number still 

 apply for all 2, but are allowed to vary with time, providing a separate solution in 

 each small window in time (Fig. 1.2). 



