Preferably these basic cost factors should. be established in the same units as 
are used for the expression of production rates (e.g. man-hours or -days, 
equipment-hours etc.) 
B. Production rates: 
  
Production rates must be established by & careful statistical analysis of work 
carried out over longer periods, so as to represent normal production routine. 
Production rates are influenced by factors belonging to all four categories 
mentioned before. The statistical analysis should be based on logical models 
taking into account the most probable functional relationship between the 
influencing factors and the resulting production rate. 
Considerable effort will have to be spent in attempting to qualify or at least 
usefully classify the various influencing factors pertaining to the project area, 
ca 
in order to be able to predict production for other project areas (with differing 
infiuencing factors). 
2.6 Establishment of accuracy models 
  
Knowledge regarding the accuracy performance of various alternative process- 
components er sub-processes should enable the planner to determine the process 
N 
parameters in such a way as to meet the given product specifications. 
Accuracy models for pianimetry and height are required for all process components 
designed to execute those functional phases which can contribute to a loss of 
accuracy of the final product. These are: 
Determination of ground control 
Determination of minor control 
Contouring, line-plotting, measurement of spot heights and planimetric 
coordinates 
Rectification and mosaicking 
. Orthophoto production 
Contouring from drop-lines or D.T.M.'s 
Cartographic processing (fair-drawing, scribing) 
Since only a part of the resulting errors are stochastic in character (the remain- 
ing being systematic) and since correlation exists between the errors of subsequent 
processes, it is theoretically incorrect to simply add up their respective 
variances in order to derive the variance of the final product. (However, due to 
the present lack of knowledge of the actual relationships, this might often be the 
only way to deal with the problem). 
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