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pressure gauge and one differential pressure gauge along each axis. 

 The other differential transducers on each axis were installed for 

 redundancy and for the generation of higher order directional Fourier 

 coefficients. The absolute pressure transducer and one differential 

 pressure transducer along each axis (dP2 and dP3) appear to work 

 satisfactorily. The redundant differential pressure gauges dP4 and 

 dPl intermittently exhibit drift and high frequency oscillation, 

 respectively. The failure of either gauge invalidates reliable 

 generation of higher order directional Fourier coefficients by 

 conventional techniques as discussed in this paper. Accurate, 

 reliable generation of the higher order (N=3) directional Fourier 

 coefficients through the subtraction of collinear differential 

 pressure signals — similar to the generation of lower order 

 directional coefficients through the subtraction of adjacent absolute 

 pressure signals — remains questionable. 



For well-defined swell, directional spectra generated from 

 the signals of dP2, dP3, and the absolute gauge correspond well with 

 the directional spectra generated from the signals of dPA, dP3, and 

 the absolute gauge. There is less agreement for poorly-defined sea. 

 Directional estimates made without the absolute pressure gauge 

 signals are generally unreliable using techniques discussed in this 

 paper. 



