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The main advantage of the method over alternatives involving physical
meetings is the lower cost. A much wider international WG can be
involved at a very reasonable cost. As all members of the WG are
volunteers the motivation level is high and much work is done in
members own time. It has been found that an occasional telephone call
or a visit can stimulate the WG when the more abstract ideas need
clarification.
Early work. The WG was formed early in 1979 and the 1st circular issued
in May 1979. Unfortunately shortly afterwards key members of the ITC
inner group were obligued to stop work on the project because of the
pressure of other duties (*) at ITC and in effect the project went on
ice until mid 1981 when active work restarted.
The 1st circular proposed a plan for the establishment of cost models
which envisaged collecting data for production processes over a wide
spectrum of the surveying and mapping scene. When the response to the
1st circular was analysed it was very clear that if we had dealt with
so many production processes simultaneously we would have created an
information explosion and meaningful analysis would have been very
difficult if not impossible. As a result when active work restarted in
mid 1981 a phased approach was proposed and accepted by the WG.
The phased approach. To be able to manage the considerable amount of
data that will be generated, the mapping process has been split into
basic phases which are essentially self-contained and each will be
handled separately. The following basic phases will be considered:
stereo plotting (conventional and digital)
primary data acquisition (aerial photography and auxiliary data for
mapping purposes)
aerial triangulation
field survey (ground control including signalization, field
identification, completion and verification)
photomap production (orthophoto and conventional rectification)
cartography (including reprographics and printing)
For each phase funtional production processes will be identified
together with all cost generating sub-processes for technological
alternatives. The individual cost generating sub-processes will be
identified in such a way that all possible combinations of rates can be
recombined and the resulting aggregated values should be of maximum
benefit to individual organizations and to the photogrammetric
community as a whole.
If one takes, for example, the orientation process from the stereo
plotting phase, the orientation process can be broken down into three
sub-processes, inner orientation, relative orientation and absolute
orientation. While some organizations will have data on all three sub
processes others will only have data on the aggregated orientation
rate. The model is therefore being designed to be capable of dealing
with both cases and with other similar recombinations. In this way it
will be possible to utilize the maximum amount of statistical data from
widely differing organizations.
At the same time as the main functional production processes and sub
processes are being determined, the factors which influence production
rates are identified. It is then possible to create a relation matrix
linking the influencing factors with the production processes (Jerie,
1976).
(*) Prof. Jerie was acting Rector at the ITC during this period