Comparison with other families of theoretical spectra 

 This composite spectrum can be compared with the families of theo- 

 retical spectra derived by Darbyshire [1955] and Roll and Fischer [1956]. 

 In both cases the agreement between the computed spectrum and the theo- 

 retical spectrum is pooro There is no value for the wind speed which will 

 give agreement between the theoretical curves and the numbers given in 

 Table llolO., These comparisons are discussed in greater detail by Neu- 

 mann and Pier son [1957a] and Neumann and Pier son [1957b]. 



Removal of white noise from the directional spectrum 

 Upon summation around semicirclesj the predicted effect of the white 

 noise was verified and the original estimate of the error in the spot height 

 readings as made by the Photogrammetry Division of the Hydrographic Office 



was verified^ The total contribution of the white noise to the E value for the 



2 2 



waves under study is thus about 1.08 (ft) , and 1.08/800 (ft) must be sub- 

 tracted from each value of the energy spectrum obtained from sunnnaing the 

 values of U2 aCtsS) and Uo^-fr, s)^ after correction for column noise. This 

 amounts to 0,00135 (ft)^ per unit square in the spectral plane. Since only 

 four significant figures were tabulated either 0,0013 or 0.0014 was sub- 

 tracted from each particular square. Each of the above values was subtracted 

 an equal number of times so as to even out the total effect to 1,08 (ft) . A 

 few very small negative values occurred due to extremes of sampling vari- 

 ation in the white noise where it was a large part of the total contribution. 

 The negative values were removed by "borrowing" from nearby points. 



218 



