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4 Establishment of Production Standards 
Production Standards should be seen as statistically derived data con- 
cerning the materials required and the personnel time and equipment time 
spent in realising a particular production unit (eg square kilometre of aerial 
photography flown, an aerially triangulated model, etc). Their derivation 
therefore requires that functional relationships be established between the 
materials and times required to produce the unit on the one hand, and the 
large number of factors which influence the production (such as scale of 
photography, density of details to be plotted, method and equipment used, 
etc) on the other hand. 
In the following, attention will first be focussed on the derivation of 
Production Standards and then on their application in planning operations. 
The first step in the establishment of production standards is the 
identification of the sub-processes for which standards are required. As an 
example, figure 4 illustrates a generalised project structure, the main sub- 
processes involved, and their internal relationships. 
In practice, however, the generalised project structure shown in figure 
4 is complicated by the following two circumstances. In the first instance, 
most planning operations require that alternative project structures be 
investigated and therefore production standards will, in principle, also have 
to be established for all likely alternative sub-processes. 
The second aspect concerns the fact that many of these sub-processes 
have, in turn, to be broken down into smaller units (sub-sub-processes), 
whereby production standards are now required for each unit. To give an 
example, the production standard for the sub-process of stereoplotting 
could be modelled so that separate units are not only established for the 
phases of relative orientation, absolute orientation, plotting, editing and 
fair drawing, but also that the plotting phase is further differentiated by 
establishing units for the various categories of features to be plotted such 
as contours, hydrographic features, roads and railways, buildings, vegetation 
boundaries, etc. The application of such a differentiated model in which the 
terrain is classified according to the density of various types of feature classes, 
will certainly be easier and more reliable than with a single overall density 
classification for terrain type. Furthermore, the investigation of the influence 
of alternative procedures will also be more convenient the greater the