7. Use number at the right of the profile to indicate the estimated accuracy of the vertical 

 distance in inches. 



8. Label doubtful profiles with "?" at the left. 



9. Leave the masked portions of the profiles blank. 



10. Indicate the dimensions of the sea surface over which the profiles have been drawn. 



PROCEDURE FOR SELECTION OF PROFILES 

 TO BE ANALYZED 



Each set of profiles should be analyzed separately. The procedure is as follows: 



1. Record the date and time of observation and any other pertinent information. 



2. Label the most distant profile with the number 1 and the succeeding profiles 2, 3, 4 

 . . . n. Profile 1 is the first useful piece of information. 



3. Compare Profile 2 with Profile 1. If there is a distinct similarity in shape between 

 them for a distance greater than one-half the length of Profile 2 (for a noninterrupted distance), 

 then discard Profile 2. Next compare Profile 3 with Profile 1 and test for acceptability in the 

 same manner. Some Profile k is eventually examined which has the property that nowhere 

 does half of its length coincide in shape with Profile 1. Profile k is the second usable piece 

 of information. 



4. Compare Profile k -t- 1 with Profile k in the manner described, and continue the process 

 until all profiles have been exhausted. The net result is p usable profiles, where p 5 n. 



PROCEDURE FOR DATA REDUCTION FROM WAVE PROFILES 



All the profiles from one pair of stereophotographs comprise a set. All the sets which 

 pertain to the same sea state comprise a group. Analyze each set separately. 



On the first profile draw a horizontal line which, as nearly as possible, divides the 

 wave record in half. This line may be thought of as mean sea level. 



Definition of Large Wave Lengths 



Beginning from the left, the horizontal line is crossed by portions of the profile which 

 have alternately negative and positive slopes below the line and vice versa above the line. 

 This creates bounded areas which possess minima and maxima. 



1. Above the horizontal line mark with an x the greatest maximum in each enclosed area, 

 below the line mark with an x the lowest minimum in each enclosed area. 



2. Record and number the horizontal distances between successive minima in every other 

 column of a data sheet. These will be the lengths of the predominant waves. 



3. Label the columns "relative wave length." 



40 



