A B €
Control distances dist. Distances + GCP’s
first best best low med. best
Unknown 698 606 594 642 618 543
parameters
Number of 2668 1620 | 1473 1738 1311 1076
observs
Number of 199 181 176 186 181 161
points
Number of 14 9 9 12 1H 9
images
9, (mm) 163.2 38.5 27.0 26.7 18.7 152
Number of 1 1 2 4 3 2
cameras
Principal 80.02 83.4 77.4 71.7 80.16 78.7
distance 83.6 88.6 84.05 84.6
values 176.7 184.18
(mm) 71.4
Mean
RMS for 0.25 0.12 0.10 0.11 0.09 0.06
XYZ (m)
It is obvious from this table, that some of the results are just
adequate for the required product. The adjustments in group A,
i.e. those with the assumption that only one camera lens was
used, are justifiably the worse. Although the overdetermination
of the system is advantageous, the fact that the image scale
presents such differences prohibits an accurate solution. One,
however, may see from the best results in this group, that an
RMS of 0.12m may be achieved, although 181 points were used
in this case.
As for group B, although two cameras are input as unknowns,
the results, as far as accuracy is concerned, are not much better.
The major improvement is observed in group C, where a few
points provide more rigid information about the reference
system. One may observe that the best results are achieved
when two camera lenses are assumed, although it seems more
logical that the second case (i.e. with three camera lenses as
unknowns) is the most realistic one.
4.4 Final products
The points determined were by no means enough for the final
drawings. It was decided to keep 188 points in total, most of
them (161) from the best adjustment of group C.
:
Figure 3: The final drawing of the roof tops
For the production of the final drawings the following
procedure was applied. Firstly the points determined were
plotted at the desired scale in order to provide a rigid frame for
the details to be added. By suitably inserting the already
produced drawings in the AutoCAD environment and using
simple descriptive geometry rules the various details could be
determined, as crossections of perpendiculars from the
corresponding points on the elevations. In Figure 3 the final plot
is presented.
5. CONCLUDING REMARKS
It has been shown that it is possible to adjust even the most
difficult configuration of images provided a suitable
combination of ground control is applied. The completely
unknown interior orientation was confronted with success,
although one is not quite sure that the resulted values for the
principal distances are exactly the true ones, as there were not
enough control points available for a full self calibration.
Moreover it was not possible, under these circumstances, to
include radial distortion terms as unknowns.
An important conclusion is that irrespective of the image
geometry, a solution was almost always possible. The photos
were taken from different heights with different inclinations.
The sketch in Figure 4 shows the relationship of the camera
stations and the axes attitudes in respect to the main object.
Figure 4: Camera axes attitudes
References
Georgopoulos, A., Karras, G., Makris, G.N., 1999. The
photogrammetric Survey of a Prehistoric Site undergoing
Removal. Photogrammetric Record 16(93): pp. 443-456, April
1999.
Kruck, E., 1998. BINGO-F v. 4.0 User's Manual.
Modatsos, M., 2000. Photogrammetric exploitation of non
metric images with analytical methods. Diploma Thesis, Lab. of
Photogrammetry, School of Rural & Surveying Eng., NTUA (in
Greek).
Stambouloglou, E., Chavakis, L, 1999. Adjusting terrestrial
non-metric images using the BINGO-F software. Diploma
Thesis, Lab. of Photogrammetry, School of Rural & Surveying
Eng., NTUA (in Greek).
—362—
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