wave by stereophotography. That is, a dominant wave could be selected 

 in the stereo pair, and it could be followed along the crest until its 

 highest part was found. The crest- to- trough height would then be 

 found at this point. A large number of such observations could be 

 made. The average of these values would then give some sort of 

 average height. 



Similarly, when a wave observer looks out over the sea surface, he 

 tends to look at the highest part of each of the short- crested waves 

 within his field of view. His eye skips about over the sea surface, 

 and thus the values recorded are similar to the values described 

 above. 



The theory of the distribution of the values obtained in the observation 

 of the highest part of each of the short- crested waves in the field 

 of view of the observer has not yet been solved. The theoretical proba- 

 bility distribution of such heights is vinknown, and it appears that it 

 ^vill remain unknown until sonne fundamental problems in time series 

 are solved. 



If the theoretical properties of an observed set of values are unknown, 

 the observations are for all intents and purposes useless. To report 

 that the average height of the waves as observed by this technique 

 is so many feet does not permit an estimate of the higher waves or 

 of their frequency of occurrence. 



Most observations of wave heights at sea do not even possess the 

 property of being the average of the highest part of each short- crested 

 wave in the field of view of the observer. They are even cruder 

 estimates of the "significant" height as made by looking out over the 

 sea surface and guessing as to a characteristic height of the waves. 

 Such estimates are unreliable because they depend subjectively on 

 the observer and on the type of ship from which the observations 

 are being made since the scale of the waves relative to the size of 

 the ship influences the observer's choice of the characteristic height. 



From the above discussion, it would appear that either just looking 

 at the waves and assigning a characteristic height or just writing 

 down a few heights of waves scattered about over the sea surface 

 and computing the average is not an adequate method of visual ob- 

 servation. Knowledge of the wave height distribution, of the errors 

 inherent in the sample size, and of source of observer error must 

 be developed theoretically in order to make the interpretation of 

 observed wave heights reliable. 



