ANALOGUE AND DIGITAL METHODS IN ARCHITECTURAL PHOTOGRAMMETRY
Astori B., Bezoari G., Guzzetti F.
Politecnico di Milano
D.LLA.R. - Sezione di Rilevamento
Piazza Leonardo da Vinci 32
20133 Milano - Italy
ABSTRACT
A description is given of an experience of the survey of the Santuario di S.S. Vittore e Corona in Feltre (province of Belluno,
Italy) of the XII century. After having obtained all drawings by traditional methods of surveying and photogrammetry, one
has wished to use procedures based on the digitization of the photographic images combined with vector elements. The used
computer programs are Orthomap and Archis of Galileo Siscam, running a high end hardware platform, in the environment
of personal computers.
Key words: Experience, architectural, orthoprojection, vector data, raster data.
1 INTRODUCTION
The fast developments of software and hardware are
stimulating the market with a series of potential
applications, also in the photogrammetric field. Most of
all, the processing of raster images questions on the
possibility of digital photogrammetry. In the field of
architecture, and especially in countries with a large
architectural heritage like Italy, the use of the metric
quality of photogrammetry often remains scarse, caused
also by the interpretation, carried out at by the operator
during the plotting stage. The possibility to complete the
the metric results with a series of qualitative data, which is
present in the photographs, can develop the relevance and
the usefulness of photogrammetric studies.
Not being experts in informatics, it was decided to acquire
experience in the sector by carrying out a series of tests in
the field of architecture with digital image processing
programs like Orthomap and Archis marketed by Galileo
Siscam, and by them kindly made available to us, together
with the necessary hardware.
The material, which has been used, had previously been
processed with traditional techniques in the framework of
an agreement between the Politecnico di Milano and the
Sovraintendenza ai Beni Architettonici of the region
Veneto to carry out a survey of the Santuario dei S.S.
Vittore e Corona at Feltre (Bezoari, Guzzetti, 1992)
(Astori, De Vincentis, 1992).
In the following two different experiences are described,
of which the first was carried out wit a part of the survey
of the sanctuary's interior with the program Orthomap,
while the second saw the use of the program Archis for the
processing of the photographs taken of the sanctuary's
exterior.
2 EXPERIMENTATION WITH THE PROGRAM
ORTHOMAP
2.1 The available material
For the described tests a total of six colour photographs
have been used, which were taken with a Rollei 6006
camera (format 6x6 cm^), which correspond to a single
view of the sanctuary's interior, and have been used for
the assembly of a longitudinal section (fig. 1). Of these
photographs, two have been taken in order to carry out
controlled rectifications of the walls of the attic, while the
other four form two stereocopies of a part of the walls of
the interior of the church. For each photograph, a
necessary number of control points has been determined.
Still in the framework of the mentioned agreement, after
the controlled rectification of the images of the attic, two
plots were made of the interior with a Wild BC3
stereoplotter, in order to represent the major architectural
lines. Besides, use was made, for the complete assembly of
the considered longitudinal section, a survey of the profile
obtained by surveying methods using a Wild DIOR 3002.
The phase of surveying for the determination of the points
and for the measurement of the sections have been carried
out with respect to a principal network, and are therefore
referred to a single reference system.
The coordinates of the surveyed points, generated in an
Autocad 10 environment, together with the plotting
results, have thus given rise to a series of vector based
drawings. These, together with the various rectified
images, turn out to be the outcome of a traditional survey.
For the described experiment, two D.T.M.s were created
(with a regular grid with a step size of 30 cm),
corresponding to two stereo models together the file with
breaklines, using the Digicart 40 analytical plotter of
Galileo Siscam.
2.2 The program Orthomap
The program Orthomap of Galileo Siscam allows for the
realisation of — orthoprojections and controlled
rectifications from imagery files of the .TIF format, which
are converted internally to a suitable format. Currently,
image processing is in black and white. A user friendly
guiding menu allows for:
a) the capturing of a D.T.M. and corresponding
breaklines for the production of an orthophoto;
b) the use of data files relating to necessary ground
control points;
c) the use of a procedure for editing of vectors on
the imgage, which results from processing;
d) the assembly of mosaics of several processed
images;
e) the superimposition on the images of vector data
determined in the same reference system; :
f) the reprocessing of the images modifying the
original grey levels and equalizing them with an
approprate editing.
2.3 The scanning of the image
One photograph of each of the two stereo copies and the
two images of the attic have been digitized by a scanner,
the latter for the realisation of a rectified image. It worth
noting at once that it not necessary to have photographs
taken perpendicular to the photographed object. For
processing with Orthomap, any arbitrary inclination is
allowed, even those in beyond the characteristic limits of
traditional optical-mechanic rectification and orthophoto