2. STATE OF THE ART AND PRESENT PROBLEMS 
A first comprehensive report on photogrammetric block adjustment 
with additional correction parameters was presented at the Ottawa 
Congress 1972. The authors Bauer and Müller were able to show 
results, by which the efficiency of simultaneous self calibration 
was demonstrated impressively |8|. Two years later, at the 
Commission III Symposium in Stuttgart several papers on this 
topic were presented. Bauer, Brown I9], Schut l10| , Salmenperä, 
Anderson and Savolainen |11| reported on self calibrating bundle 
adjustment and Ebner and Schneider presented a first application 
to independent model block adjustment |12|. 
Although simultaneous self calibration today is recongnized as 
the most efficient concept for compensation of systematic errors 
in aerial triangulation there are essential problems which still 
have to be solved, Three main problems can be distinguished here. 
The first one concerns the proper choice of the additional para- 
meters. As a study of the above mentioned literature shows, the 
individual authors are still experimenting with the number and 
type of correction terms. Furthermore it is noticed, that the 
additional parameters are treated as block invariant terms. This 
means, that identic systematic deformations are supposed for all 
images or models of the block. This supposition however, is only 
correct in case of really homogeneous projects (one camera, film, 
measuring instrument and so ory In all other cases a variation 
of the systematic errors within the block must be expected. 
Summarizing it can be stated, that a general concept for the 
choice of correction terms is still missed. Such a concept would 
require several different groups of additional parameters and a 
sufficient number of effective parameters per group. 
The second problem follows from the fact that highly correlated 
or insignificant additional parameters lessen the block stability 
and change the accuracy of the adjusted block coordinates to the 
worse. Therefore the algebraic correlations between the individua 
correction terms and the correlation with the orientation para- 
meters should be as small as possible. The significance of the 
computed correction terms can be checked by proper statistical 
tests. If some of the additional parameters are found insigni- 
ficant the block adjustment should be repeated without them. 
Although these requirements are known in principle, frequently 
not enough attention is payed to them in practice. 
The third problem is a purely operational one and concerns the 
comfort of self calibrating block adjustment programs, In the 
opinion of the author the user of such an extended program 
shouldn't be burdened with the selection of the additional para- 
meters and the critical valuation of their amounts, as computed 
by the adjustment, Consequently this task should be automized 
as far as possible, | | 
  
The following chapter contains recommendations for a solution of 
the problems quoted above, For that purpose a strategy is sugge- 
Sted, consisting of a sufficiently general functional and stocha- 
stic model and of proper significance tests, In that way self 
calibrating block adjustment shall be standardized to a certain 
extent and the practical application shall be simplified.