a variance-covariance analysis is carried out. Simultaneous adjustment should give the most unbiased 
results. 
Presented papers 
H. Meixner introduced his presented paper **A Universal Computer Programme for Analytical Aerotriangula- 
tion”, describing the adjustment programme at Stuttgart. Attention was drawn to the high rate of convergence, 
and thus low computer time, even with large blocks. (i.e. OEEPE Test, Oberschwaben, 208 photos). 
T. Schenk introduced his presented paper “Investigation into the Condition of Normal Equations in Block 
Triangulation by the ‘bundle’ Method’. Considerations include the relative merits of iterative or direct 
methods, and precision of computation (stability, rounding errors, etc.). 
Monday July 31 1972, 9:00 
Invited Paper: “The Use of Auxiliary Data in Aerial Triangulation’ by J.M. Zarzycki. 
Panel discussion 
E.H. Thompson (President). Economy has been mentioned, but this should not precede technical requirements. 
I ask the panel to consider all aspects. 
H.H. Schmid. Aerial triangulation comes within the field of interpolation, especially with non-vertical 
photography. Auxiliary data provides additional geometrical data, but needs to be used simultaneously in the 
adjustment. There are photographic errors (i.e. refraction near the aircraft) which are not easy to introduce 
in any conventional way. The inclusion of auxiliary data in an adjustment does not produce mathematical 
problems, but weighting is an important matter if the data is not to upset the internal geometry. 
M. Cunietti. We have limited experience of instruments other than statoscope and solar periscope. One thing 
is clear in Zarzycki's paper, that there has been no recent improvement in the accuracy of auxiliary data 
equipment. All the effort seems to be towards photogrammetric application, not improvement of the actual 
data. Current situations can be improved if we concentrate on more refined equipment like that used on the 
moon, and we should be looking to the future. 
JM. Zarzycki. More accurate systems are very expensive, and I have concentrated on those which are more 
likely to be economical. Somehow we must greatly reduce the ground control requirements in remote and 
inaccessible areas. I agree that auxiliary data should not be reduced to each photograph, but should be applied 
through some form of smoothing procedure. I, too, am concerned by the lack of improvement in instruments, 
but I did not cover this as it is a Commission II matter. 
G.H. Schut. Based on our experience at NRC in the use of APR, I agree with Zarzycki that APR and statoscope 
can considerably reduce the ground height control requirements. The APR data should be introduced in the 
adjustment stage, rather than in the triangulation stage. We get a satisfactory height adjustment by using the 
APR height data in a smoothing procedure. Similarly, clearances can be used in a smoothing procedure to 
determine scale to an accuracy comparable with that of an adjustment, whose polynomials and a liberal amount 
of ground control are used. It is surprising that so little use has been made of auxiliary data. 
It is not correct, as Zarzycki stated, that the use of polynomials introduces a significant geometrical 
deformation into individual models. This use causes problems at the compilation stage, only in the case of a 
poor fit between strips because of the meaning of the co-ordinates of tie points. 
H.G. Jerie. I reported 4 years ago on this subject, and I am disappointed to see no advances. Only APR is used 
to a large extent, and only for large projects. Schmid is right in saying that the geometry of the bundle is 
imperfect, but most users seek a lower precision in which this is barely significant. 
LS. Jacobs. One reason for not using auxiliary data is the existence of adequate control. 
H.H. Schmid. When seeking accuracy of 4 or 5 pm there is little scope for auxiliary data, but in the 15 jum 
range there is more application. 
P.R.J. Boniface. In answer to a remark by E.H. Thompson, in my design for a solar periscope, two small 
cameras are linked back to back, and exposed simultaneously with the survey camera to which they are