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6.3 Computation Methods 



The LFI method for an array of pressure measurements can be broken down into 

 the same sequence of steps as with the analysis of a water surface array: 



1. Pre-processing of record. 



(a) Determine estimate for level of noise in the record. 



(b) Determine MWL and subtract hydrostatic pressure from the records. 



(c) Determine estimate for magnitude and direction of Eulerian current. 



(d) Define a set of continuous records from each gauge from the discrete ob- 

 servations by cubic spline interpolation. 



(e) Specify spacing of output locations. 



(f) Compute mean zero crossing frequency. 



(g) Non-dimensionalize record and all parameters. 



2. Primary values of numerical solution parameters are chosen. 



(a) Window width (tq) 



(b) Order of solution (J) 



(c) Number of time samples of the pressure records within each window (/) 



(d) Number of water surface nodes within each window (M ) 



3. Global solution is computed on an entire wave to provide first estimates for 

 local optimization 



4. For each selected output location, a window in the record is defined, and an 

 LFI solution is computed. 



(a) Initial guess for the optimization determined from the global solution. 



(b) Full nonlinear optimization for all unknown components of the potential 

 function is computed. 



