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The most universal, on-line subsystem for compilation of detailed information 
directly from aerial photographs is the one configured around the versatile 
and accurate analytical plotters. The part of the subsytem concerned with 
the compilation of information on elevation could exploit specialized 
automated analytical plotters with high speed  scanner-correlators for 
generation of digital terrain models. The collected data could be fed 
directly into the external storage devices of the land information system via 
an interactive editing facility. The feedback from the editing facility for 
digital terrain models allows the addressing of areas where the corrections 
should take place, directly in the model space. In general, during the 
performance of correction routines, the analytical plotters of the subsystems 
are under human control. For correction of some errors, such as the eventual 
gaps in the automatically recorded digital terrain models that can be 
discovered only after the completion of compilation from a number of stereo- 
models, the models in question can be readily reconstructed from data in the 
"control files". If required, the contours are normally derived from the 
digital terrain models by an independent, off-line, numerical-to-numerical 
conversion. 
The part of the analytical plotter based subsystem concerned with the 
information on features operates under human control since the requirements 
for interpretations and decisions in the course of feature compilation is too 
complex for a technologically and economically viable automated control of 
processes. Considering the ease with which the analytical plotters and 
interactive editing facilities can be interfaced and the potential for the 
enhancement of the editing routines by the use of editing techniques 
available on analytical plotters, this type of feature compilation subsystem 
offers the best editing capabilities among all the possible configurations. 
Expanded by an automatic facility for numerical-to-graphical conversion, this 
type of subsystem also allows for an efficient exploitation of data in the 
data base of the land information system, for generation of various line- 
drawn graphical outputs such as cadastral, topographical, soil and land use 
maps. 
An alternative configuration of the subsystem for compilation of detailed 
information from aerial photographs is the one based on hybrid instruments 
with analog plotters as elementary components. This type of subsystem, 
although viable, is, in general, less universal and less flexible. The 
decrease in compatibility between the hybrid and the digital system 
components is mostly felt in the areas of orientation procedures, interface 
with editing facilities, reconstruction of models, feedback of information 
into the original records and automation of processes. 
If the accuracy of stereo-orthophotos fulfills the requirements of a land 
information system, then, the subsystem for compilation of detailed 
information may be composed of stereocompilers and instruments for generation 
of stereo-orthophotos. The most efficient variant of a stereo-orthophoto 
subsytem is the one with automatic stereo-orthophoto generating components 
equipped with on-line scanner-correlators that are capable of performing the 
auxiliary pictorial-to-numerical conversion required for the printing of the 
stereo-orthophotos. Besides simultaneous printing of  orthophotos and 
stereomates, these components perform the role of the subsystem for 
compilation of information on elevation by automatically generating the 
digital terrain models. If necessary the contours can be, in this case, 
generated again by an independent numerical-to-numerical conversion using 
the computing facilities of the land information system. Being in principle 
analytical instruments, these components can also use the adjusted