14 
taken in colour. The corresponding figure in 1971 was 18 % The 
reason for the decrease is that experience has shown that black 
and. white film is as good as colour film for mapping of ordinary 
details and contour lines. Due to its lower price the black and 
white film has therefore reduced the use of colour film. The ad- 
vantage of the colour film is however obvious for mapping objects 
such as manholes, sewage pipes etc. These objects can be pre-mar- 
ked in different colours and are then easily identified on the | 
colour images. | 
Automation has been applied to many stages in the mapping process. 
Several investigations have been carried out. 
The development of the digital terrain model has advanced to the 
stage where the photogrammetric problems can be considered solved. 
Research is to-day concentrated on data systems and digital out- 
put in & form attractive for the users. € e 
The Geographical Survey Office is developing methods for topogra- 
phic mapping using numerically controlled methods. A D-Mac pencil 
follower was used for digitizing, point by point for symbols and 
straight lines - and with time intervals for irregular map ele- 
ments. The map size was 50 x 50 cm. 
The subsequent computations had to take into account the trans- 
formation of data to the common system, to identify colour sepa- 
ration sheets and map symbols, to generalize, to state tool po- 
sitions and to delete erroneous data. The cost for the computer 
work was about US dollars 140. \ 
a 
Kingmatic Mark III was used for The automatic plotting. It can 
interpolate straight lines, circles and parabolas.