) 4 
14 
Table 3. Photogrammetric Instruments Used in Production 
Type Number 
1968 1969 1970 1974 
Comparators - 1 1 1 
Precision plotters 75 74 74 7.1 
Topographic plotters 51 52 51 50 
Orthoprojectors 1 1 1 1 
Rectifiers 2 2 2 2 
Aerial cameras 5 8 8 8 
Terrestrial cameras - 2 2 1 
Automatic developers z 4 5 2 
Automatic co-ordinato- 
graphs 5 5 4 5 
Automatic co-ordinate- 
printers 42 14 15 16 
The largest development has taken place within the field of 
orthophotography. In 1969 the Zeiss-Gigas Orthoprojector at the 
Geographical Survey Office was equipped with a prototype optical 
interpolator and an electronic contour line device. One year la- 
ter the first production devices were installed. The strip width 
which initially was 2 mm could be increased to 6 mm. This reduced 
the time for differential rectification of one model from about 
4 hours to about 1.5 hours. At the same time the discrepancies 
between the strips were eliminated and the accuracy was in- 
creased. 
An economically favourable method has been developed for the 
revision of orthophotomaps. This method allows the use of the 
profile plates from the first map production to be used at the 
revision of the photomap. 
Increased use has been made of small desk computers at map pro- 
duction. Thus numerical methods are often used at the relative