-12- 
• • 
A procedure involving the determination of the planimetric co-ordinates 
of all exposure stations by airborne trilatération would probably also 
involve quite some logistic complications, as all ground stations which 
are required for a sound geometrical determination of the exposure 
stations have to be manned and equipped during the whole period of 
aerial photography. Considering the possible meteorological hazards 
involved in aerial photography, the author feels that in this way the 
difficulties of the work are shifted from the office to the field, which 
is certainly not the generally accepted aim of photogrammetry. 
These data might, however, be profitably employed to improve the 
absolute accuracy of single strips, which is much lower than in the case 
of a block. 
From the above, it is clear that auxiliary data will primarily be used 
as a means of controlling the height accuracy. 
The general characteristics of the accuracy of camera orientation 
elements determined from auxiliary data compared to the accuracy of 
elements derived from aerial triangulation are given in a schematic way 
in table 3. 
In the author's opinion, there still exists a tendency to consider the 
auxiliary data as a substitute for the determination of camera orien 
tation elements rather than as a means of improving the overall accuracy 
of the final results of the aerial triangulation. This scheme, however, 
illustrates the advantages of utilising auxiliary data in the adjustment 
phase of aerial triangulation as opposed to their direct application in 
the instrumental phase. These differences will be treated in more detail 
in Chapter IV. 
The economical consequences of using auxiliary data in aerial triangu 
lation are summarised in table 4° 
Economical consequences of the use of auxiliary data 
•Additional costs for obtaining 
• Saving in ground control 
auxiliary data due to 
• Possibility of using smaller 
equipment 
photo scale results in saving 
operation 
in 
reduction 
cost of aerial photography 
•Additional costs because of 
cost of aerial triangulation 
modification of AoT. procedure 
cost of restitution 
complications in adjustment 
Table 4