. However, a rough
or these photos was
istances appearing on
were these particular
hem to the best of our
ment method, which
practically everything,
This method is none
1. As output products
n points, co-ordinates
; and, of course, the
eras used. In such an
vailable would be of
ware was available. It
ire with long presence
The characteristics of
| observations
ation
letic measurements in
tive of their attitude
ts
niques
dons, as the software
ell known collinearity
image co-ordinates of
on the images, the co-
the eventually known
and all the necessary
" the camera (Kruck,
co-ordinates of the
's attitudes expressed
e co-ordinates of all
nt and — if so required
erior geometry of the
efficients of the radial
1ates of the principal
preparation stage was
enlarged and used in
ch would be necessary
eration resulted to a
s constructed with the
t also with the help of
the immediate knowledge of such a complicated monument.
Hence a total of 242 points were determined, necessary to
provide a firm basis for the final drawing. These points
appeared on at least 2 images and at maximum on 12.
The co-ordinates of these points could not be determined from
the existing elevation drawing, as these were in rotated systems.
Hence three dimensional distances between almost all of the
points could only be determined from the work completed so
far. It is obvious that in this way all possible geodetic
measurements were made available for the adjustment.
The above described image data were scanned at a resolution of
1200dpi on an AgfaScan desktop scanner, thus resulting to a
pixel size of 21pm, which corresponds to approximately 85mm
on the ground. It was thought that although the use of a simple
off-the-shelf scanner could introduce geometry errors, these
would be adjusted later. In order for the image co-ordinates to
be measured a simple own developed software (Stambouloglou
et al. 1999) was used. With this software one may perform all
the necessary measurements within the AutoCAD environment
and receive as output an ASCII file with the image co-ordinates
referred to the principal point.
All the determined points were marked on all images they
appeared and then the measurements were performed. As for
the interior orientation, the knowledge that the negative size
was the standard 26x34 mm was used. Approximately 1200
measurements were necessary for this task. The RMS errors for
each affine transformation and also the number of observations
for each image are given in Table 1.
Image RMS error (um) No of obs
1 26 59
3 34 91
4 20 64
5 10 116
6 18 78
7 15 129
8 6 120
9 3% 46
10 37 66
11 111
12 3 86
13 7 56
15 41 117
16 2 67
Mean 17 1206
Table 1: RMS errors after the affine transformations and
number of observations for all images used
4. DATA ADJUSTMENTS
4.1 Input files
BINGO-F requires two input files. One file, image.dat, contains
the image co-ordinates as measured. The other file, geoin.dat,
enables the user to fully control all parametrs involved. It was
decided to variate several parameters for the adjustments.
Firstly it was obvious that the images were taken with a zoom
lens, which actually could be interpreted that practically every
image was taken with a different camera. Hence the camera
constant and the position of the principal point should definitely
be included in the unknown parameters.
As already mentioned, BINGO-F may adjust a photogrammetric
network without any ground control points, under certain
circumstances of course. Additionally either distances between
points or geodetic co-ordinates would enhance the strength of
the adjustment. Hence the kind and the quantity of the ground
control was another interesting subject for variation during the
adjustments.
4.2 Performing the adjustments
The adjustment was performed dozens of times. As experience
was gained, it was decided to group the calculations into mainly
three groups.
Firstly it was assumed that there was one single camera used
throughout the project. Hence all photographs were included
into the adjustment with one unknown principal distance.
Approximately 25 known distances provided the necessary
ground control. Successive minor variations to the data were
required in order to exclude points giving unacceptably large
residuals, or even exclude a couple of images, which would not
fit into the adjusted network.
The main problem encountered was the resulting reference
system. As already mentioned, BINGO-F has the ability to
calculate initial approximations automatically. This is carried
oout by the module RELAX, which actually assumes that the
initial reference system is the one defined by the fisrt two
images in good geometry. If, later, known ground control points
are fed into the adjustment, this system adjusts itself to the
desired one. If, however, this is not the case, the initial
reference system remains unchanged.
Secondly the images were grouped according to their scale.
Assuming that the camera was equipped with a zoom lens, it
was decided to introduce to the adjustment two camera
constants as unknowns. The point distances provided the
necessary ground control.
During the adjustments corrections were made to the initial
approximation of the camera constants of the two "unknown"
cameras, in order to achieve a more reliable solution. Again the
problem of the uncontrolled determination of the co-ordinate
reference system was a major problem.
Finally it was decided to carefully choose three points and with
the help of the corresponding distances assign to them
rectangular co-ordinates, in order to force the software to
provide adjusted co-ordinates in that particular system. Seven
additional points were also used as vertical control, in order to
ensure the horizontality of the system. In this way the resulting
system was closer to reality and enabled the easier exploitation
of the results.
4.3 Discussion of results
The most important results of the adjustments are grouped and
presented in Table 2.
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