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A) Use of auxiliary data as a substitute for ground survey techniques 
Here the main consideration is the application of APR to provide height 
control as a substitute for ground levelling. 
Although of limited accuracy, the technique can be extremely useful if 
height control is required for existing survey photography. 
The possibility of using smaller aircraft and lower flying heights and 
the reduced requirements with respect to meteorological conditions 
(cloud cover) offer many economical advantages. 
In the case of extremely small scale photography (taken from large 
flying heights), the use of APR profiles along the lateral overlap of 
this photography (with additional cross profiles for the purpose of 
network computation)will most probably yield better results than could 
be obtained by aerial triangulation. 
Furthermore, the following equipment can also be listed under this 
heading; Hiran, Shiran, Aerodist for the purpose of airborne trilaté 
ration (by line crossing method) and the use of Shiran, in connection 
with the inertial platform, for the determination of secondary plani 
metrie control. 
B) Use of auxiliary data to control aerial photography completely, 
eliminating the necessity of aerial triangulation 
An effort in this direction is the design of the AUQ-28 system. 
The economic justification of such an approach is only possible if the 
cost of obtaining auxiliary data with the required accuracy is lower 
than the cost of the execution of aerial triangulation. Consideration 
must, however, be taken of the fact that further developments of the 
aerial triangulation technique (in methods and equipment) will result 
in a considerable reduction of the unit cost for this operation, 
C) Application of auxiliary data to aerial triangulation 
A distinction can generally be made between the use of auxiliary data 
employed for the determination of planimetrie control and height control. 
For the first alternative, the use of radar clearances (as a means of 
controlling the scale) and the group of equipment Hiran, Shiran and 
Aerodist (as a means of controlling the planimetrie position of the 
exposure stations) is theoretically possible. 
However, there does not seem to be much advantage in considering this 
with the possibility of using planimetrie block adjustment methods, 
which yield a higher relative accuracy and at least the same absolute 
accuracy as can be obtained by the use of these auxiliary data.