EVALUATION OF RELIABILITY OF VISUAL ESTIMATES OF WAVE HEIGHT 



The U.S. Naval Photographic Interpretation Center and the U.S. Navy Hydrographic 

 Office utilized the stereophotographs from the UNIMAK and the VALLEY FORGE to produce 

 the sea surface profiles illustrated in Appendix A. From these profiles, wave height data 

 were determined as discussed in the section on "Sea Surface Profiles" and tabulated in 

 Table 4. Note that this table includes waves associated with sea conditions in which seas 

 predominated, others in which swells predominated, and still others in which both seas and 

 swells were present. 



The characteristic wave heights obtained by the shipboard observers are compared 

 with those derived from the stereograms for the same sea condition in Figure 6, where values 

 from Columns 7 and 9 of Table 4 are plotted as abscissas and ordinates, respectively. If 

 exact agreement existed between visual estimates and the results of photogrammetric analy- 

 sis, then all points would lie on a straight line with a 45-deg slope. The points plotted in 

 Figure 6 scatter fairly well about a straight line which has a slope somewhat greater than 

 45 deg. The average deviation of the points from the line is expected to decrease as the 

 number of points is increased. It should be noted that each stereophotograph covers a limited 

 field of view compared with the field of view of the shipboard observer; see Figure 7 for ocean 

 areas included in the camera perspectives for both ships. 



It is considered that Figure 6 shows good correlation between the visual estimates 

 and quantitative height determinations made from the stereophotographs. Individual estimates 

 may not be accurate, but when the number of estimates is large the correlation is good. 



Scale 

 1000 ft 



Scale 

 1000 ft 



\ 1650 ft 

 from Cameras 



UNIMAK CAMERAS See 

 0.026 Square Miles 



Figure 7 - Ocean Perspectives Seen by Stereocameras on UNIMAK and VALLEY FORGE 



Areas indicated are fixed by properties of cameras, film, stereoplanigraphs, and camera separation. 



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