2.5. Extended application of aerial triangulation 
Within the conventional scope of aerial triangulation for 
medium scale topographic mapping we can first state a consi- 
derable improvement of accuracy, reliability, and economy. 
Modern aerial triangulation has become a simple and regular 
operation. 
Genuine extension has taken place in aerial triangulation for 
small scale topographic mapping (1:50 000 and 1:100 000) 
leading to a new level of economy by reduction to minimum con- 
trol both for planimetry and height. High expenses for ground 
control can be balanced by blocktriangulation of large, or 
even very large blocks. 
At the large scale end of the range of application aerial trian- 
gulation has become firmly established as precision method for 
large scale mapping and for numerical determination of coordi- 
nates. Such applications refer to cadastral Surveys, planning 
of road construction, and large scale precision mapping in 
general. They are of special interest also in regions of well 
established geodetic networks up to 3rd order, because of the 
homogeneous accuracy of aerial triangulation and its indepen- 
dence of local control. The results are very well comparable 
with fully controlled single model restitution. 
In addition, the extreme accuracy capabilities of selfcali- 
brating methods qualify blocktriangulation as a method of point 
determination of its own and open up new and independent geo- 
detic application for network densification and traverse 
networks. Particularly interesting is the combination of photo- 
grammetric network densification and photogrammetric cadastral 
Surveys in a joint system. 
Finally it should be mentioned that the introduction of nume - 
rical methods has opened up the application of triangulation 
techniques in the fields of non-topographic photogrammetry, 
for instance in architectural photogrammetry. 
3. Digital terrain models, image processing, and 
  
geometry of remote sensing 
  
According to the new, rather general definition the interests 
and claims of Commission III extend into many fields of photo- 
grammetric activities. Mathematical methods, data processing, 
software, and accuracy are terms which increasingly mark 
essential features or necessary tools of many working proce- 
dures and applications. 
Up to now, three main areas have evolved to be treated by 
Commission III. They are areas of active technical development 
for which special technical sessions are reserved at the 
Helsinki congress, for presentation of papers and due dis- 
cussion,