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lead us, however, into the domain of geodesy proper. In pur
suing the purpose of this presentation the emphasis is on
the analysis of such photogrammetric operations and results
which reflect into the general area of precision photogrammetry.
1. The Method of Photogrammetric Satellite Triangulation
The geometric principle of photogrammetrie satellite
triangulation can he explained in several ways. Similarly,
depending on the professional background of the experimenter,
the data acquisition method as well as the mathematical
formulation of the data reduction procedure will differ. Most
obvious is the difference in approach between the astronomer
and the photogrammetrist. The astronomer is inclined to favor
rather long focal length in order to increase the precision
by scale at the expense of the geometric strength inherent
in wider viewing angles. Haunted by his experience with the
problem of "seeing" the astronomer favors observational systems
which track, more or less exactly, the motion of the object
to be photographed, in order to make possible rather long
exposure times, thus integrating the image forming process in
order to reduce the scintillation effect. The astronomer applies
predominantly a data reduction process in which the interpola
tion of the unknown target image (satellite) into the reference
frame (known stars) is obtained by the so-called plate con
stant method. This is essentially a fractional linear trans
formation augmented with higher order terms, the free variables
of the solution being coefficients whose precise physical
meaning in terms of instrumental constants and geometrically-
defined orientation elements remain obscured.
The photogrammetrist--as well as the geodesist--is more
likely to favor fixed cameras because of his concern about
the stability and control of tracking instrumentation,
especially in programs requiring extended field operations
under conditions far removed from the astronomical observatory
environment. Particularly the photogrammetrist is inclined
to sacrifice some focal length to gain increased geometrical
strength from a correspondingly wider bundle. Certainly he
is sold on the need to introduce into the data reduction pro
cedure mathematical models which simulate the photographic
recording process by parameters with distinct geometrical and
physical meaning. In principle the mathematical formulation
for the reduction of photogrammetric satellite triangulation
is the same as for aerial triangulation, or for any three-
dimensional triangulation scheme based on- photogrammetric raw
data.
The reduction consequently is based on the condition
of collinearity, expressed by a simple transformation relating