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instruments than on the actual purpose of the survey. A certain
link to the requirements of society can be found in many instruc
tions for cadastral surveys, where different accuracy requirements
are prescribed for e.g. rural, semi-rural and urban areas. In the
technical manual of the Netherlands cadastre W. Baarda made a
further stepthe accuracy specifications for survey lines and lowest
order traverses may be made dependent on the precision with
which marked boundary lines, e.g. ditches or hedges, can be identi
fied and defined. In an intuitive way this has probably often been
done by good surveyors, but the directives mentioned work out
the principle on a rational and quantitative basis. It must be said
that there are difficulties attached to the assessment of the uncer
tainty implied in a given type of boundary, and still more to the
question how far the type of boundary mark gives an indication
of the utility of a boundary strip of land for the proprietor.
In "higher" geodesy viewed as a pure science, and in science in
general, it seems virtually impossible to attach utilities to different
outcomes of decisions such as accepting or rejecting hypotheses.
In the design of plane or geodetic control networks there always
is an element of economy, and there usually is a somewhat closer
connection to the needs of society. But in general they serve many
purposes and it remains very difficult to find an objective measure
of utility: what is the loss of utility if a trigonometric point's
coordinates are 10 centimetres wrong, or i meter? But a question
which also arises is whether accuracy requirements should pertain
to coordinates, or to coordinate differences, or to angles and distance
ratios computed from coordinates. Once questions like these have
been answered, the next one is what instruments and methods
should be used and what shape the network to be established should
have. The question how one makes the most efficient use of available
instruments and methods calls again for decisions; the relevant
study might properly be called operations research.
In an excellent chapter on models, Chernoff and Moses [3]
say the task of constructing adequate workable models seems
to be a major aspect of the "art" in the various sciences". Mathe
matical and computational techniques have the full attention of
geodesists but the decision-theory approach raises the question
whether a realistic model for utility in geodesy can be made.
Summarizing, decision theory is important for geodesists in that
it provides a clarifying view of statistical methods, and in that it
requires a complete specification of all the factors in a decision
problem, thereby tending to stimulate what might be called "ratio
nal behaviour" in geodesy.
References:
[1] Bazhanov, K. V., The use of linear programming methods in the
organization of geodetic field work. Geodesy and Aerophotography 3
(1963) page 169.
