A.Capra 
NON-CONVENTIONAL SYSTEM IN UNDERWATER PHOTOGRAMMETRY 
Istituto di Topografia, Geodesia e Geofisica Mineraria, Universita di Bologna. 
Viale Risorgimento,2- 40136 Bologna, ITALY 
Abstract 
The non-conventional monoscopic photogrammetric systems have been recently developped: they 
permit a low cost aquisition and data reduction, with an adequate accuracy in object coordinates 
in terrestrial and close range photogrammetry. 
The results of experiments with one of these systems in underwater photogrammetry are here 
presented with particular attention to obtainable accuracy. 
Key words 
Photogrammetry 
Introduction 
The employment of non-conventional 
monoscopic photogrammetric systems of data 
reduction has been remarkably developped in 
the latest years. 
These systems have a low cost of aquisition 
(are utilizable with metric and non-metric 
cameras) and a low cost of data reduction ( 
they cost about 10 times less than a classical 
analytical reduction system). They are 
photogrammetric multi-image restitution 
systems that permit 3-D mesurements of an 
object or of a structure. The system is 
composed by a PC computer ( a good 
configuration is with microprocessor 386 ), 
a digitizer and a reduction software ( fig. 4 ). 
The photograms are measured on a digitizer 
tablet in monoscopic way. We know or we can 
determine the interior parameters of the 
cameras. Using these parameters and some 
known points in the photograms it is possible 
to make the relative and the absolute 
orientation. 
We obtain the 3-D coordinates of the real 
points of the object through a projective 
transformation by pointing out on the 
digitizer the omologous points in the different 
photograms. 
It is possible with these systems to 
reconstruct an object in 3-D coordinates with 
a good accuracy ( few centimetres) in object 
Non-conventional Monoscopic Analytical System 
Non-metric cameras Underwater 
coordinates at different photographic scales 
in terrestrial and close range 
photogrammetry. 
The author made some different applications 
of one of these systems with non-metric 
cameras in underwater photogrammetry using 
an appropriate methodology. 
The aim was to determine the accuracy of 
the method, that has been tested comparing 
the coordinates obtained throgh 
photogrammetric mesurements and the known 
coordinates of the control points of a 
reference frame 
The experiments have been executed with an 
apparatus manageable and relatively easy to 
use. Underwater non-metric cameras Nikonos 
with three different focal lenght (15 mm,28 
mm and 35 mm) were utilized. So it would be 
possible to control the accuracy of the results 
versus the lens also used. A reference frame 
of reduced sizes containing the control points 
of known coordinates was used. The non- 
conventional monoscopic photogrammetric 
system was the Rollei Metric MR2 . 
The accuracy obtained could show the 
possible fields of underwater applications of 
the particular adopted method.