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REPORT OF COMMISSION VII 91 
sively industrial, maritime installations and railways, the knowledge of which 
is essential to the photo interpreter. 
Finally the photo interpreters should be trained to prepare various types of 
photographic documents and to prepare intelligent specifications for photo- 
graphic missions. 
THE PREPARATION OF PHOTOGRAPHIC DOCUMENTS. 
The principal types of documents which may be requested are the following: 
(a) Single vertical photographs or stereoscopic copy: to be done on large 
scale on certain details of special topographic or war interests, which one wishes 
to study separately. 
(b) Vertical series or strips; always occuring with a superposition of 60% 
to allow a stereoscopic examination. To be rectified in case the requesting party 
should need it for certain topographic purposes. 
(c) Mosaics: to be used mounted or unmounted. In the first case if employ- 
ed in the place of the topographic chart, the mosaic may be rectified in order to 
measure and to print over it the kilometric grid, some indications concerning 
*toponomastics" and all the marginal indications referring to the represented 
terrain and to the procedure used for the rectification (topographic chart of 
reference-topographic coordinates of reference, graphic of union, scale, etc.); if 
used to supply the headquarters with a clear view of the whole of the enemy's 
and one's own situation in a specified sector the mosaic may not be rectified, 
and with the predetermined conventional symbols all the details of military 
nature which are of interest will be pointed out. In the second case: the mosaic 
is made by a simple joining of photographs placed in progressive order and sub- 
divided by series into envelopes or boxes. The headquarters or branches will 
mount, according to each case, the whole or a part of the mosaic, making to 
coincide with pins the common details of the individual photographs. This type 
of mosaic has the advantage of offering to the observer a view of the whole, 
and at the same time, breaking it down into parts, to allow the stereoscopic ob- 
servation of details which are of greater interest. 
For the indication of natural or artificial details of the separate photos wc 
consider it useful to use conventional grids printed on plastic materials (dyrite, 
copyrite, etc.). Such grids may be used for photos of different sizes and offer 
the advantage of permitting reference to the photographs without putting signs 
above the indications which might cover interesting details. 
TYPES AND TECHNIQUES OF MILITARY PHOTOGRAPHIC INTERPRETATION. 
Marine Photo Interpretation (Shipping, ports, harbors, etc.). In identifying 
types of vessels from aerial photographs the interpreter should have at his dis- 
ions showing the main characteristics of these 
posal necessary tables and publicati 
vessels. Ship identification as to type usually can be accomplished by observing: 
1. the length-beam ratio; 2. the wake; 3. the disposition of the main calibre ar- 
tillery; and 4. the superstructure characteristics. 
Port and harbor photo interpretation aims to supply data about the possi- 
bility that the area offers as a shelter for the maintenance and repair of ships. 
It also should provide specific information relative to: 1. the receiving capacity 
of the harbor; 2. the commercial value of the harbor; and 3. the presence or ab- 
sence of dock-yards. The interpretation of such facilities as cranes, grain ele-