In all cases GEOSCAN employs the same adjustment algorithm. Therefore a user 
has to learn the program only once and will be able to compare different types of 
networks satisfactorily. 
GEOSCAN consists of four main modules (figure 1). 
  
PREPROCESSOR 
  
  
  
LEAST SQUARES/STATISTICAL TESTS 
— mem — 
men 220) a 
  
  
  
PRESENTATION/ANALYSIS 
  
  
  
CALCULATION DF TOPOGRAPHIC POINTS 
  
Figure 1: Main structure of GEOSCAN 
3.1. The preprocessor 
The preprocessor is a users-friendly interactive module which creates, controls 
and manipulates the inputfiles, needed for the adjustment. Therefore these files 
are computable in the adjustment step causing neither singularities in the normal 
matrix nor uninterpretable data-snooping results. Since all input and configuration 
errors are detected interactively in this preprocessor a considerable reduction in 
editing-time can be obtained. Figure 2 shows the structure of the preprocessor. 
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