SYSTEMATIC DEFORMATIONS OF PHOTOGRAMMETRIC BLOCKS CAUSED BY UNDETECTED
GROSS ERRORS IN THE TERRESTRIAL CONTROL NETWORKS
T. Bouloucos *, M. Molenaar
* International Institute for Aerospace Survey and Earth Sciences CITOS
Enschede, The Netherlands
Agricultural University
Wageningen, The Netherlands
ABSTRACT
The connection of aerotriangulation blocks with the ground coordinate
system is traditionally done by control points for the planimetry posi-
tioned at the perimeter of the block and with several chains of height
control points over the block. The distribution of control points is
quite adequate with respect to precision, as the vast research and prac-
tical experience over the past 20 years has shown. The required
configuration of control points in block adjustment may, however, lead
the surveyor to compute coordinates of points from a weak network, weak
with respect to precision and, most important, to reliability, i.e., the
ability to detect gross errors. In such weak networks, undetected gross
errors in the survey measurements may seriously effect the coordinates
of the control points with which the photogrammetric block has to tie-
up. The photogrammetrist (who has great difficulty in detecting gross
errors in given control points) using the most sophisticated methods of
block adjustment may eventually arrive at incorrect conclusions during
the evaluation of the results and distorted final coordinates of points.
In attempting to monitor these problems, we have formulated some direc-
tives for the design of an integrated point determination system.
1. INTRODUCTION
In an earlier paper /13/, one of the authors discussed the effect of
errors in a ground control network on the final results of the adjust-
ment of an independent model block. There it appeared that, even in a
relatively small block, large observational errors in the ground control
network could slip through easily and cause large distortions in the
photogrammetric block. This is especially true if the control network
gives support to the block only at the perimeter. In this paper, we will
consider a similar case in a bundle block and see to what extent self-
calibration techniques can be used to compensate such a systematic -
like distortion. The example is based on a simulated block and geodetic
network. The adjustment of the network was made with ITC’s NETADJUST
program package /5/. The block adjustment was made with the PATB program
from Stuttgart.
2. THE BLOCK AND THE NETWORK
Figure 1 shows the generated block and network. The block consists of
five strips with eleven photographs each. Each photograph has nine
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