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PRECISION IN CASE OF COMBINED POINT DETERMINATION
Henk de Heus
Delft University of Technology
Department of Geodesy
Thijsseweg 11
2629 JA DELF T, The Netherlands
ABSTRACT
Land surveyors have made significant progress in the optimization of control net-
works. For the purpose of testing and describing the precision of coordinates
artificial covariance matrices have been developed.
In photogrammetry too much attention is paid to the precision. However, these in-
vestigations are mainly restricted to the photogrammetric precision influences, as
they neglect the stochasticity of the terrestrial control points.
In this paper the combined influence of the two on the precision of the final coor-
dinates is described. Some ideas concerning a modified artificial covariance
matrix for constrained control networks are included in the precision description
of coordinates resulting from the photogrammetric block adjustment.
1. INTRODUCTION
In the Netherlands the adjustment, testing and quality analysis of terrestrial
control networks is carried out in two phases:
l. asa free network (phase I)
2. bij connecting the free network to known points (constrained network,
phase II).
The main advantage of this procedure is a seperation of the statistical testing for
outlier detection. In a free network adjustment possible (measuring) errors in the
observations can easily be detected, because the mathematical and stochastical
model of the free network are well defined. In this way the data-snooping can not
be hampered by possible complicated distortions of the known points and the
generally only roughly known variance covariance matrix of the given coordinates.
In the second phase only the coordinates of the known points are still to be tested.
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