Conclusions 
The method applied allowed to obtain an 
accuracy of 1-3 cm in object coordinates at 
the photographic scale from 1:40 to 1:100.The 
image distance and the scales used are the 
most significant in sea water where in 
average conditions of visibility the very high 
adsorption and scattering, that reduce the 
light transmission, do not permit an 
appropriate illumination and resolution for an 
iobject distance more than 3-4 m. 
The accuracy obtained is good , in fact the 
values are near those declared in terrestrial 
photogrammetry standard application with 
non-conventional systems. 
The data aquisition is relatively simple. It is 
sufficient to use non-metric cameras and a 
reference frame at a low weight and of 
reduced sizes. Using only few points ( 8 in the 
experiments)  self-calibrating and bundle 
adjustment reduction program it is possible 
to obtain the tested accuracy. 
There was not a significant difference in 
accuracy using different focal lenght. The 
cameras did not take photos exactly at 2 m. 
distance and the photograms with different 
cameras had not been taken in the same 
environmental conditions, but with different 
refractive index. 
So we should conclude that we can 
reconstruct in 3-D coordinates an object at 
image distance approximately fixed, using a 
number of variable photograms and changing 
the focal lengths and the sea water 
conditions. The variation in accuracy is not 
very significant ( 1-3 cm.), relatively to 
standard underwater applications. We have 
only to collocate a reference frame in the 
field of the photograms without using control 
points on the object or on the structure. 
The method presented could be employed to 
reconstruct the form and the dimensions of 
particular undersea object or structure. In 
particular it is interesting when the subject 
has a long extension in one dimension, for 
example to survey an archaeological site or to 
map the sea bottom. 
The fig. 6 shows some indicative profiles in 
a frontal and in a lateral view of the cave and 
of the stalactite of photograms of fig. 5. 
These profiles have been obtained in Autocad 
utilizing the X,Y,Z coordinates of the 
photogrammetric reduced points. 
This paper showed the results of first 
experiments of the method, some others 
experiments with different systems and 
methodology are going to execute, which 
results will be published successively. 
240 
Acknoledgements to Geotop s.r.l. ( Ancona , 
Italy ) for Rollei MR2 photogrammetric 
reduction system loan. 
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Photogrammetric