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New perspectives to save cultural heritage
Altan, M. Orhan

CIPA 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey
In all building surveys, 3d object information is reduced to a
minimum of points. From those points, a data structure with
predefined geometrical elements can be derived. In this
research, point coordinates were derived through total station
measurements and multi-image photogrammetry. Total station
measurements have supplied control point information. Multi
image technique has been applied while taking metric images.
This has provided ease in selecting camera positions. In addition
to these two surveys, digital images were taken for producing
the texture of the building model. The process of the field
survey is explained in the below under two headings:
measurement of control points and image acquisition.
3.1 Measurement of Control Points
All elevations were surveyed with total station. It was decided
to measure minimum six evenly distributed points for every 33
by 14 meters. In other words, the long elevations were divided
into three measurement areas and the short ones were
considered as single measurement areas. Then, a polygon was
inserted around the building (Figure 2). The control points on
the elevations were connected to the polygon through a series of
measurements, x, y and z values for each selected point were
measured. All this measurement process included the facade
area up to the entablature zone. The recessed roof portion was
3.2 Image Acquisition
In this step, criteria for selecting metric and digital cameras, and
taking photographs were developed.
3.2.1 Camera Selection: A comparison of image formats
and resolution after film-scanning presents that medium format
metric cameras are the best ones suitable for building
recording (Pomaska, 1998). Image formats in the range of
60mm x 60mm are known as medium format cameras. Such
cameras provide metric solutions using a reseau. The widest
known metric camera for close range applications is the
Rolleiflex 6008 metric. It is a reseau camera with 121x121
crosses; mesh distance 5mm. This camera is the ideal solution
for photogrammetry in cultural heritage recording (Pomaska,
2001). On the other hand, digital cameras are time saving
devices for detailing the building models produced on the basis
of surveys with metric cameras (Grussenmeyer, et all, 2002).
Digital cameras are still in a rapid development process.
Today, digital cameras known as SLR (Kodak Blue Plus Color
Full Frame) are of importance for architectural photogrammetry
(Pomaska, 2001).
Figure 2. The polygone and the coordinate system established
around Defensionskaserne.
In the case of Defensionskaserne, Rolleiflex 6006 metric
camera and Kodak DCS 290 are used, respectively. They are
not the state of art at present, but they were the ones available in
hand and they are sufficient for the job. Kodak 400 ASA film
was used. With Rolleiflex 6006, metric recording of the
building was carried out. Then, the model produced on the basis
of the data collected with Rolleiflex 6006 is textured by the help
of digital images taken with Kodak DCS 290.
3.2.2 Development of a Strategy for Taking Photographs:
The strategy for taking metric and digital images were
developed separately. For metric images, it is known that multi
image technique is easy to handle on site. Camera stations can
be selected without restrictions. Total station measurements
supply control point information in a unique coordinate system.
Complex buildings can be recorded with several separated
image bundles.
It was decided to survey only the decorated east elevation of
Defensionskaserne in detail. This means multi-image technique
was applied only here. As explained for the control point
measurements (see section 3.1), this long elevation of nearly
100m was divided into three parts named as left, middle and
right. It is known that bundling all the images together should
be preferred for the success of the adjustment. However, the
division of the long facade into three parts has some practical
outcomes. It becomes possible to work on every part separately.
This means the opportunity of different people working on
different parts. At the same time, it becomes easier to make the
bundle adjustment since the number of images is decreased.
The position and direction of middle format cameras were so
organized that the facade whole was covered (Figure 3). It was
important to shoot two images for each building component to
be measured. A third image was preferred to provide control
information. While shooting these images that cover up the
same area to be measured, correct definition of the intersection
angle between the shooting directions gains importance. That
means the intersection angle should neither be very acute nor
obtuse, but it should be around ninety degrees. This angle
selection does not only goes for xy plane, but also for zy plane.
At the end of this survey, close up images at human scale and