CI PA 2003 XIX 11 ' International Symposium, 30 September - 04 October, 2003, Antalya, Turkey
requirements, processes and techniques called for are similar to
those found in the fields of surveying, construction research,
archaeology, the history of art and architecture, as well as in the
care and preservation of monuments. A common starting point
is a graphical survey. Our aim, therefore, is the conception of an
integrated building information system, combined with a
digitally-supported survey.
2.1 Capture and Structure
The starting point for the conception of an ordering system was
to achieve the maximum generalisation whilst not ignoring the
complexity and specificity inherent in architecture.
Principal emphasis is laid on the systematisation of the built
structure of a building, and the establishment of relevant
planning and use-related information. Taken into account are
the planning methods of architects working in the field of
building restoration and reconstruction.
A typical problem when surveying existing buildings is that a
large amount of information is recorded without an overview of
the overall situation. The tendency is to concentrate on details,
whereby more straightforward structural connections within the
building remain overlooked. These problems can be countered
through the use of an ordering system that is used from the
outset.
The basic principle is a room-by-room process. Buildings are
perceived as a series of different rooms, each room being a
functional unit in itself. The appearance of a room is described
by its surfaces. Built elements can be described as material
'rooms', defined by their surfaces.
There are two primary ordering principles:
(A) Room structure - the spatial subdivision of the buildings
complexes can be arranged both as entire buildings or
individual rooms, and
(B) Element structure - the hierarchy of built elements in the
building that which defines space and from which the geometry
of the building is measured.
The project takes the approach that there is no generally
applicable building model. The aim is instead to provide the
user with appropriate tools to adapt a flexible building model to
the specific situation at hand. The coupling of dynamic data
structures with static basic structures allows flexible models to
be adapted using fixed algorithms.
informal data relational data
Figure 1. Information container
formal data
width: 1 2
height 4.0
depth: 1.2
information
geometric data
A series of attributes and their range of possibilities were
identified, based upon practical experience in the field of
architectural surveying.
The following are examples of object properties and
characteristics relevant in working with existing buildings:
method of construction and material
building damage and extent of damage
constructional qualities
colour
historic information and value etc.
Nevertheless, the architectural survey tends to concentrate on
the geometric qualities. We have developed four different levels
of abstraction corresponding to the phases in architectural
practice (fig. 2):
taxonomy or icon oriented (level 1)
sketch orientated (level2)
2D-plan orientated (level3)
3D-model orientated (level4)
These correspond to the individual phases in the surveying
process.
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Level 1 : taxonomy
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Level 3: 2D-plan oriented
Level 2: sketch
Level 4: 3D-model oriented
Figure 2. Different levels of detail for describing building
substance (in this case building geometry)
2.2 Complex digital building models
The computer-supported building survey is not simply a
geometric description of a building. It should also provide a
multitude of features and characteristics relevant both to the
buildings future use and to its later CAD processing.
In addition to surveying geometric data, formal (specific
building data), informal (text, images, sketches etc.) and
relational data (probable structural relationships) can be
captured. The captured data is stored within an information
container that can be used within both the spatial structure as
well as the building element structure (fig.l). Geometric data is
“only one attribute” of such an information container.
3. PROTOTYPICAL IMPLEMENTATION
Based upon the analysis and the identification of deficiencies, a
hypothetical system was developed with the aim of providing a
set of tools for the computer-assisted surveying of buildings.
This developed prototype-software 'freak 1 illustrates the path
from sketch to measured 3D-model (fig. 3). The user initially
creates a three-dimensional sketch of the object to be surveyed
which provides a rough topological and geometrical direction.
Through the addition of measurements, for instance through
tacheometry, photogrammetry or manual measurements, the
sketch takes on more and more of the actual situation up to a
given degree of accuracy. This process is assisted through the
use of geometrical constraints, for instance parallel surfaces etc.
