CIPA 2003 XIXInternational Symposium, 30 September - 04 October, 2003, Antalya, Turkey
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Fig. 1.8 Top view of the "very low altitude photography crew"
Fig. 1.9 Part of a 2D-Photomap of the historic site of the Jewish
Cemetery in Magdeburg (Germany)
2. New Perspectives for Processing Single Images in
Conservation.
It is liked to point out, the signalization of controlpoints partly
can be replaced by (digital) photographs of the queue of ground
survey points, when engaged with the reflectorstaff. These
controlpoints, can be clearly interpreted on the snapshot and
transferred to the corresponding synoptic photograph for, e.g.,
rectification purposes. It is also very important, clearly to assign
the point number on the picture, at least by voice recording for
moving sequences.
The use of single images in conservation can benefit from
existing digital imageprocessing devices and suited software, as
well as (still?) from analog rectification devices. For low
attitude values the latter even could be overhead or slide
projectors.
A new way to visualize the projection theory can be derived
from the French facet method. The facet method has been used
in France until about 1970 in an analogue manner, even for
precisely cadastral mapping purposes. The characteristic terrain
surface is adapted by multiple polyeder projection.
For a modem flexible application of a modified facet method, in
particular to survey an Archaeological site, the “polyeder” can
show a regularly (4 x 4m) grid as well as random edges, see
Fig. 2.1
- The edges of these polyeder pattern are marked with wooden
colored sticks.
- The object surface must be suited to be adapted by a polyeder
pattern
- The three dimensional coordinates of the regular or non
regular situated edges of the polyeder pattern are set out and/or
determined using the conventional terrestrial polar surveying
method.
- Extremely low altitude aerial photography, successive taken
with a amateur camera from a telescope beam of approximately
10m height, must show the particular polyeder or grid plain of
about 4 x 4 m in nature, as indicated by at least 4 corresponding
marked points of the polyeder respectively of the grid.
The exposure is verified from the ground using modem
infrared control or ball exposure.
Continuously the images, defining the polyeder, will be
digitized and digitally rectified, based on at least 4
controlpoints, e.g., using the Rollei MSR rectification
program.
Of course an alternate method is analog optical
rectification using a rectifier.
Finally the rectified images are digitally or manually
mosaiced to achieve the complete
Fig. 2.1 Principle sketch of the modified facet method for
obtaining a rectified photo mosaic by approximating the object
surface with a regular and/or non regular grid pattern and
successive processing of digital or analog image rectifications
Fig. 2.2 Differentiell rectified Orthophoto of the excavating
situation in 2001, based on the principle of the facet method
(see fig. 2.1), as carried out by B. Luebbehusen, who mosaiced
about 80 rectified single images showing a 4 x 4 m grid
