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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.