3.3 Positioning data versus attitude data 
By examing case 1 and comparing the cases El, E2 and E3 
(table 2), it is evident that camera position data are 
more effective auxiliary data than angular data. The 
results obtained with positional data alone (E2) are not 
much improved (<10%) by additional attitude data. This 
outcome is confirmed by simulation case  E3, with 
attitude data only. The resulting block accuracy in this 
case is very much poorer, compared to the block accuracy 
achieved by positional auxiliary data. However, there is 
one important exception. If attitude data are very 
precise (<lmgon) they become very effective and they can 
replace even precise position data. The results converge 
to the same values. This also explains the still 
noticable difference between El and E2 on the high 
precision level Pl for auxiliary data (see fig. 2). 
3.4 Block size 
There is a slight effect of block size. The larger the 
block the more effective are auxiliary data on the same 
level of precision (Fig. 7). The effect is especially 
visible as long as the precision of auxiliary data is 
poor (> 1 m) and if no ground control is used. The de- 
toriation of smaller blocks is quite insignificant, how- 
ever, and may be disregarded in first instance. 
Remark: The various simulation cases are valid not only 
for the actual assumptions. If all precision assumptions 
are transferred to weight ratios, the results can be 
related and interpolated to other photo sales and other 
measuring accuracies. 
4, Conclusions 
  
The simulation studies presented in this paper have 
shown the attainable accuracies in aerial triangulation 
by joint block adjustment including navigation data. The 
influence of camera position data on the accuracy of 
photogrammetric blocks is considerable. They allow in 
any case reduction of control to the minimum case (CL). 
Already camera position coordinates observed with low 
accuracy (t 10 m) allow aerial triangulation with 
minimum ground control and provide ground point position 
accuracies which could otherwise only be reached with 
quite dense ground control. 
Precise attitude data («10 mgon) combined with camera 
position data provide additional improvement of block 
adjustment. The use of precise measured rotations alone 
combined with sparse ground control (Cl) is also 
possible. Those conclusions may be important, as the 
determination of position and attitude data require 
different hardware systems. 
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