By designing the computer support sensibly the speed of certain ope- 
rations can be considerably increased. This applies to orientation, sampling 
for DTM aerial triangulation, etc. 
The overall accuracy and comprehensiveness of data can be increased 
by on-line detection of gross errors, corrections for deterministic errors, and 
application of the method of least squares. On-line monitoring of accuracy 
permits to adapt the measuring process to specifications. 
The acquired raw data can be conditioned, i.e. converted into a more 
useful form of further use. Examples are co-ordinate transformations, data © - 
editing, compression, interpolation, compilation of partitioned data, etc. 
By inspecting the listed capabilities of the computer supported instru- 
ments, it appears that they approach the capabilities of the fully-digital type 
systems. À closer examination of the two equipment classes shows, however, 
that the computer supported conventional instruments are slightly less 
versatile, less flexible and less stable than their fully-digital counterparts. 
However, they are faster at plotting due to freehand tracking in planimetry 
(which has not yet been provided in fully-digital type plotters). Moreover, 
computer supported conventional instruments cost less and their main parts 
can operate independently. This, however, permits to carry out different 
operations by different equipment components simultaneously. 
For applications demanding a very high accuracy, flexibility and/or 
versatility fully-digital type systems are preferable. The anticipated advan- 
tages of the computer supported conventional instruments will presumably 
be diminished by introducing somewhat simplified, less versatile and thus 
less expensive fully-digital type systems. Hence, a point might be met in the 
not too far future, when the capabilities and prices of the two systems will 
be in balance. From that point onwards development will presumably be in € e 
favour of the fully-digital type systems. 
Acknowledgements 
The author wishes to thank Dr.Ing. P. Stefanovic and Mr. F. Gouds- 
waard for the careful reading of the manuscript of this paper and their 
valuable comments.