1 
TRENDS IN DESIGN OF DIGITAL EQUIPMENT 
FOR PHOTOGRAMMETRIC INSTRUMENTS 
By 
U. V. Helava 
Bendix Research Laboratories 
Southfield, Michigan 48076 
U.S.A. 
ABSTRACT 
Digital equipment has been incorporated in some photogrammetric 
instruments for many years; much more of it will be seen in future in 
struments. The reasons are primarily economical. The designers of 
photogrammetric instruments must be able to make full use of rapidly 
advancing digital technology to transfer to the instrument user full 
benefits of the progress paid for by other parts of economy. This paper 
reviews the use of digital equipment in photogrammetry as well as the 
trends in general digital design and explores where such trends may lead 
in photogrammetry. The conclusion is that the designers of photogram 
metric instruments are confronted by significant challenges in meeting 
their future responsibilities. 
The continued advances in photogrammetry are primarily due to the 
development of more accurate and efficient instruments. Today, as never 
before, we have an unparallel opportunity to use and exploit new tech 
nology that will yield more cost-effective instruments. The future of 
our profession and its role in the world economy depend largely on how * 
we pespond to this opportunity. 
SCOPE OF DIGITAL FUNCTIONS IN PHOTOGRAMMETRIC INSTRUMENTS 
With the notable exceptions of mechanical structures to carry the 
photographic film or plate, and of optical viewing, nearly all functions 
needed in a photogrammetric evaluation instrument can be replaced by 
electronic or electromechanical means. While such replacement may not 
be practical at present, we must keep in mind that it is feasible, and 
thst it may even extend to mechanical structures as digitizing at the 
data acquisition level, a la ERTS, becomes better developed. Funda 
mentally then, the scope of digital functions in photogrammetric instru 
ments can be seen to be extremely wide. 
The entire scope may not be realized in the near future, if ever. 
On the other hand many digital functions are already in widespread use 
in photogrammetry. Consider the use of encoders, for example. These 
devices perform among other things, a function equivalent to measuring 
the magnitude of mechanical translation or rotation. In fact, encoders