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