New Techniques 
Traditional methods of dimensional control are being 
supplemented by techniques exploiting electronic de- 
vices. 
The pace of developing new techniques is considerable; 
a careful assessment of the field is required, in order 
to determine the most effective methods for each new 
project. 
At present we can identify three major areas of appli- 
cation of electronics in Engineering Control, that is 
digitizers, E.D.M. and computing equipment. 
A) Digitizers were initially fitted to photogrammetric 
B) 
instruments to speed up the recording of model coor- 
dinates and to generate punched-paper tape for sub- 
sequent processing by computer. 
Recently cheap camputers have become available offer- 
ing considerable speed and memory size. 
In consequence, the days of complex analogue photo- 
grammetric machines are numbered, and will be succeeded 
by campact analytical equipment. 
The choice of analytical equipment is wide. Among the 
simplest is the Zeiss Stereocord, a stereocomparator 
linked to a desk calculator. 
A more accurate, and rigorous solution is achieved with 
the Zeiss Steko 1818 and a mini-computer. This is a 
versatile, economic package which is the most effective 
for a wide range of engineering applications. 
At the far end of the scale, analytical plotters are 
available with servo-driven photo-stages and zoom ocu- 
lars, but their application is in mapping rather than 
engineering control. 
E.D.M. Early Tellurameter and Geodimeter models were 
designed for Geodetic Control. Equipment using an infra 
red carrier was introduced about 10 years ago, and has 
helped to replace low order triangulation by traversing 
techniques. In addition, mounted on a theodolite, it 
provides a rapid, precise tacheametric system for sur- 
veying detail.