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PERFORMANCE OF REDUCED AERIAL PHOTOGRAPHS IN THE MPS-2 
M.H. ELFICK 
Department of Civil Engineering and Surveying 
The University of Newcastle, N.S.W., 2308, Australia 
and 
G. FUCHS 
Central Mapping Authority 
BATHURST., N.S.W., 2795, Australia 
Commission Number:  1-V 
ABSTRACT 
Aerial photographs from a Wild RC-10 camera were reduced by 
rephotographing the negatives using a Hassablad camera with a copying 
lens. The lens distortion of the final photography was examined, and the 
accuracy of point determination measured, and compared with results from 
measurements taken from the original large format photography by the same 
operator using a Kern PG-2 analogue stereoplotter. The results indicate 
that reduced aerial photography can be used for many mapping applications, 
provided that the photographic reduction is performed carefully using a 
suitable lens, and high resolution film. The subsequent measurements then 
have to be made with a precision analytical instrument with suitabie 
magnification. 
1.0 INTRODUCTION 
The limitations inherent in mechanical analogue stereoplotters have 
greatly influenced the design of aerial survey cameras, and their lens 
systems. It is difficult to build and maintain a mechanical system to 
accurately transform from a perspective to an orthoginal projection since 
all small errors and amounts of play in the mechanical linkages tend to 
compound and affect the final accuracy. The probiem is reduced if the 
scale of the photography is kept as large as possible, and hence the 
development of large format cameras. In addition, radiai lens distortion 
has to very small to reduce the difficulties in correcting this type of 
image displacement on mechanical equipment. 
The lens designer is then faced with the difficult task of providing a 
lens system with a wide field of view and even light distribution over a 
large format image and maintain low radial distortion characteristics. 
The resultant lens systems tend to have a low resolving power and be of 
small aperture. The small aperture then influences the film and shutter 
speed and the final outcome is that most aerial cameras have a resolution 
of less than 80 line pairs per millimetre on the negatives. 
If reduced diapositives are made from large format negatives using a high 
resolution film and a special copying lens, then very little data will be 
lost in the printing process and the resultant stereopair when viewed 
under suitable magnification should appear to the operator similar to that 
viewed in an analogue instrument using large format diapositives. 
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