The software to produce 3D models must allow their storage in
a format compatible with the software used for visualisation. It
should be noticed that the great majority of software to produce
3D models also includes tools that allow their visualisation
from several view points, their animation (walk-throughs or fly-
overs) and even the production of some short films (e.g. in AVI
format).
There are several software packages available on the market,
some even for free, to visualise 3D models. Some packages
allow the insertion of additional information such as documents
of text, Ayperlinks, music and films. Different software or
modules may be used according to the model type (city, terrain
or object), and the pretended visualisation (animation, walk-
throughs, fly-overs, virtual reality or static visualisation). To
attain an adequate selection it is advisable to make some prior
tests with data sets of different sizes.
5. CASE STUDY
5.1 Objectives
The main objectives of the work address:
e Use of Photogrammetric techniques for recording of
cultural patrimony. To this end, it is produced an
architectural archive consisting of-several products, such as
images and control points, elevations of facades, and a 3D
model rendered and also in vector format;
e Production of a 3D urban model to be inserted into an
architectural archive;
e Comparison, in terms of performance and precision, of two
photogrammetric techniques (monoscopic convergent
versus stereoscopic) and of different photographic cameras
for data acquisition.
e Production of a multi-media CD-ROM containing all the
relevant information recorded of the patrimony and its
surroundings.
5.2 Study Area
The work was carried out for the mother church of Oeiras
(Figure 3a), situated in the old part of the town of Oeiras close
to the capital of Portugal, Lisbon. The church dominates the
town centre and its immediate surroundings. These
surroundings are complex due to a large number of roofs
(Figure 3b), which are difficult to interpret and, thus, require
generalisation.
Figure 3. a — Mother church of Oeiras; b — surrounding urban
tissue
5.3 Resources
The resources described here concern the software and
instruments used, and are listed in Tables 1 and 2.
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004
Instruments
Task (details in table Software
2)
Calibration of cameras: Camera
Calibrator
Image Processing: Image Analyst
; and PhotoShop
Architectural Phot hi
Archive AORTA Editing: AutoCad
Cameras
3D Urban Stereoscopic Photogrammetry:
Model Scanner Image Station SSK Pro
Visualisation Photogrammetric | Convergent Monoscopic
Station Photogrametry: PhotoModeler 4.0
Analyse of | Total Sation Geometric Modelling: Microstation
Results
Visualisation:Microstation,
Cosmoplayer and Macromedia
Director
Statistical tests: Excel
Table 1. Resources: instruments and software
Branch Focal Pixel size Image ;
Instrument distance Format | Resolution
Model (um)
(mm) (mm)
Digital Rollei
Metric D7Metri 7.5 3.5 8.9x6.7 | 2552x1920
Camera €
Digital Non- | Nikon
metric Coolpix 7.69 4.5 6.8x5.1 | 1600x1200
Camera 775
Analogue
Semi-metric | Leica R5 35 15 36x24 | 2445x1583
Camera
Analogue
Non mecttie | acia Rm [cns 20 36x24 | 1800x1200
Camera
nn
Geometric ; ;
Resolution Radiometric
Instrument | Branch (ppp) Model Resolution (bits)
PPP (intern/extern)
Scanner Epson 1600x3200 1640XL 42/42
: Branch Linear Angular Rr Te
Instrument Model Resolution | Resolution Specifcities
Total Sokkia | 2mm+2pp G n.
Station Set 600 m S ne Y Law
Table 2. Technical characteristics of the instrumentation used
5.4 Data Acquisition
Data acquisition concerns the preparations for the creation of
the architectural archive, and addresses the planning and
acquisition of the photographs/images, including camera
calibration, and of the control points. In the following sections
these two processes will be discussed in more detail.
5.4.1 Planning and Acquisition of photographs/images
Planning of the photographic survey is a crucial phase in the
overall process of creating the architectural archive for it allows
an appropriate coverage of the object at a scale that is adequate
to attain the required accuracy. It is done in different ways in
accordance with the technique to be used to extract the required
information. In the following, the planning phase is presented
for the extraction process with stereoscopic and monoscopic
photogrammetric techniques, respectively. For both techniques,
the medium photo scale has to be between 1:400 and 1:600 to
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