results of the wave pole spectrum with the stereo spectrum and verify the 

 estimate of the amount of the white noise error, 



3. Study the angular variation for bands of constant frequency. 



4. Compute the confidence bounds for the bands of constant frequency 

 and compare the frequency spectrum obtained from the directional spectrum 

 with the wave pole spectrum and various theoretical spectra. 



5. Remove the white noise from the directional spectrum and analyze 

 the spectrum both in an unsmoothed and smoothed form. 



6. Fit the angular variation for bands of constant frequency by means 

 of a Fourier series approximation and determine a smoothed analytic form 

 for the spectrum. 



7. Correct the covariance surface for the effects of column noise and 

 white noise. 



Column noise correction 



The ridge along the horizontal axis of figure 11.18 is rather well 



defined especially for U(17, 0), U(18, 0)and U(19, 0). A vertical line, say, 



along the values U(17, 3), U{17, 2), U|17, 1). U(17, 0), U(17,-l), U(17,-2), 



and U(17, -3) shows that there is a definite ridge produced by the values of 



U(17, 1), U(17, 0), and U(17,-l). The ridge is quite possibly due to column 



noise as given by the random errors, e^ > 3-^d it has shown up in the final 



spectrum as the filtered effect of the contribution of W to lj(r, s) in 



equation (11.4). By inspection, if 0,0100 (ft) is subtracted from each value 



of U(r, o) the central part of the ridge will disappear and become approxi' 



mately equal to the value of U two rows above and below the horizontal axis. 



190 



