2. PROJECT DEFINITION
The idea and the initiative of the CIPA project belongs to
Prof. P. Waldhausl (Technical University of Vienna,
Austria) and the aim was to check the current state-of-the-
art in Architectural Photogrammetry.
The test object chosen is one of the Otto Wagner's
Stadtbahn Station buildings on the Karlplatz in Vienna,
Austria. Its dimensions are 15x8x10m*. A 6-station
surveying network has been established around the
building and the polar coordinates of 44 non-signalized
(but well defined in majority) control points have been
measured. After the adjustment of the surveying
measurements, the local cartesian coordinates of the
control points have been determined with an rms values
of 2mm. These points cover all four exterior facades.
Subsequently the object was photographically covered.
During this campaign different cameras have been used
like the Rollei 6006, the Hasselbland 500 EL/M, the
Leica Elcovision, the Nikon FE2, the Pentax PAMS 645P
and ME-Super totaling to more than 70 photographs.
The photographs have been measured by different
measuring devices and the data processed by different
software packages. In total 16 photogrammetric Institutes
from 9 countries have participated to this campaign and
the preliminary results are reported in (Patias, et. al,
1995, Waldhausl and Ogleby, 1994).
However, all the results obtained up to now are only
refering to the use of analog cameras and analog
measuring devices. The purpose of this test is to show the
contribution of Digital Photogrammetric techniques in
recording architectural objects.
For this reason the same control point information have
been used but the acquired photography is in the form of
digital imagery taken by a camcorder. The measurements
of image coordinates have been performed on the
computer screen using zooming on the images. The final
results are compared to those obtained by the classical
Photogrammetric means.
Figure 1. "O. Wagner Pavillion" test object. Superimposed are
shown the check points of the first facade used in this test.
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3. IMAGE ACQUISITION
3.1 The Imaging System
The JVC GR-S77E Camcorder is an inexpensive
consumer product. It is a free-hand portable camera ang
the on-site control for the acquired imagery is achieved hy
the internal monitor. It incorporates a 1/2" (6.4mm x
4.8mm) color sensor with ca. 420.000 sensor elements.
The imagery can be directly trasmitted to a frame grabber
or recorded on a S-VHS C tape. The digitized images
have a size of 728x568 pixel, which results in a pixel
spacing of 8.5um in the horizontal and 8.3um in the
vertical direction.
Figure 2. The JVC GR-S77E Camcorder
3.2 Photography
Using such an imaging system in Architectural Photo-
grammetry requires that most of the functions which are
implemented for the convenience of the common user (eg.
autofocus, zooming functions or image stabilizer) are
disabled. In this test the autofocus was disabled and the
zoom lens was fixed at its shortest focal length. This
sytem does, however, offer the ability to store a huge
amount of data on inexpensive video-tapes and allows on-
site quality control for the acquired images.
Dealing with a low-cost camcorder instead of metric
cameras, the problem of low sensor resolution must be
faced. To obtain sufficient accuracy in object space with
such an equipment, it is advisable to take as many images
as is reasonable and to use multiple camera arrangements
with convergent rays, instead of being restricted to special
camera arrangements (eg. stereo pairs). On the other
hand, the number of measurements increases rapidly with
the number of images, but one of the advantages of
Digital Photogrammetry is that it is possible to establish
semi-automatic or automatic measurement routines.
The whole building was covered by 24 video images.
However, for the purpose of this test only 4 images
corresponding to the first facade have been used.
The average image scale of the used photographs is
approximately 1:2300 (average object distance is approxt-
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996
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