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I. Techniques of Amphibious Photographic Interpretation. 
The work of the amphibious photographic interpreter covers nearly every 
problem in photographic interpretation. He must interpret hydrographic con- 
ditions, including both wave and bottom characteristics. He must measure water 
depths. He must study natural features of terrain and vegetation on and behind 
the beach, and interpret installations in the beachhead, both civil and military. 
The techniques used, therefore, vary from simple stereoscopic examination 
to precise measurement of water depths. 
Of course it is not possible in a single paper to treat in detail all the types 
of interpretation which contribute to amphibious intelligence. Such subjects as 
beach analysis, terrain and soil prediction, vegetation interpretation and anal- 
ysis of land transportation facilities, are all major fields in their own right. 
Photographic interpretation of coasts and beaches for intelligence purposes 
is a composite of these and other specialities, and the experienced amphibious 
interpreter must be able to perform with at least moderate effectiveness in most 
of them. 
Broadly speaking, the amphibious photographic interpreter analyzes the 
photographic image in two ways — he examines it (stereoscopically and under 
monocular magnification) and he measures it. These procedures we will call 
*visual analysis" and “metrical analysis”, respectively. For convenience, they 
are discussed separately, though in practice they are often used together. 
   
Fig. 4. Onshore data derived from visual 
Fig. 3. Offshore data derived from visual 
analysis. 
analysis. 
Visual Analysis. The basic image characteristics used in interpretation have 
been given by various writers as size, shape, tone, texture, shadow pattern, and 
siting (or location). Of these, size and precise location require metrical analysis. 
The rest are normally evaluated by simple stereoscopic examination. These fac- 
tors are analyzed by the interpreter on the basis of (1) his own experience, in- 
cluding his knowledge of such things as local landforms and vegetation, military 
activity and cultural practice in the area, and (2) the experience and knowledge 
of others as available in photographic interpretation keys, intelligence docu- 
ments, and other reference materials. This background material, combined with 
common sense and a knowledge of military intelligence requirements, enable 
him to produce information on such details as the nature of the bottom, the 
53