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literature 
Preparation and measurement 
— In only a few exceptional cases were more than 6 orientation points measured 
and repeated measurements taken at a point. 
— The distribution of instruments used for the measurements was: mono-comparator 245 
Stereo comparator 41%; precision plotter 46%; topographic plotter 11%. 
Strip formation and adjustment 
— Analytical strip formation methods were used in the majority of projects, the 
percentages being: analogue 29%; analytical 39%; semi-analytical 8%. The strip 
formation phase was omitted in 24% of the projects. 
— Polynomial adjustment methods with a strip as computational unit were the most 
frequently used, the percentages for the various computational units being: 
Strip 47%; model or section 43%; plate (i.e. bundle) 10%. 
— As was to be expected, nearly all (89%) of the adjustments were performed 
numerically, as compared to 3% graphical adjustments and 8% by means of 
analogue computers. 
— Although the bridging distance between perimeter control in block adjustments 
can be expected to be fairly small, the extremely short bridging distances used 
in practical strip adjustments was surprising. A possible explanation is that 
planners tend to be conservative in order to allow for the considerable spreads 
that can occur in the results of identical projects. 
The distributions of the bridging distances were: 
Strips: 29% less than 2 models; 76% less than 4 models; 
90% less than 6 models; 97% less than 10 models. 
Blocks : 27% less than 2 models; 63% less than 4 models; 
83% less than 6 models; 93% less than 10 models. 
The estimator o1 
This estimator may be determined after a least squares relative orientation as 
the standard deviation of either the residual parallaxes or of the coordinate 
errors at model points. 
The distribution of the sample of 79 estimators, was such that o1 varied in 
magnitude between 1-12 u , with a mean value of 40 u , and with 90% of the 
estimators less than 7 u 
The estimator o; | was found to depend on the following parameters: