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Title
Close-range imaging, long-range vision

, Use of Radio.
surveying and in
lam 2000
ail Surveys with
al Sites, ISPRS
ed Surveys in
haeological Sites

FITTING, PORTAYAL AND MAPPING
FOR THE PRODUCTION OF 2" ORDER SURFACES PHOTOMOSAICS
Artemis Valanis
School of Rural and Surveying Engineering — Laboratory of Photogrammetry
National Technical University of Athens, Greece
9, Heroon Polytechniou Str., Zographos, GR-157 80
e-mail: rs97053@central.ntua.gr
KEY WORDS: Photogrammetry, Architecture, Map Projections, Surface Reconstruction, Mosaicing
ABSTRACT
The Daphni Monastery is known worldwide for its famous Byzantine mosaics. After the earthquake of 1999, the monastery suffered
serious damage and the Greek Ministry of Culture took action for the conservation of the monument. Within the frame of the
requested tasks, the laboratory of photogrammetry was assigned the task of creating very large-scale (1:5) cartographic developments
of the Domes.
Although hitherto encountered in literature, the creation of cartographic developments is not a standardized and automated process.
In addition, the demanded large-scale products called for the development of a very innovative and rather complicated approach.
In this paper a complete approach is described in order to create cartographic developments of 2"-order surfaces. The proposed
process was successfully applied in this case.
INTRODUCTION
The Daphni Monastery is considered to be one of the most
important specimens of Byzantine art and architecture and it is
known worldwide for its famous Byzantine mosaics. The
monastery was built in the 11” century and is situated in the
southeastern part of Attica near Athens. After the earthquake of
1999, the monastery suffered serious damage and the Greek
Ministry of Culture took action for the conservation of the
monument. For that reason the Laboratory of Photogrammetry
of NTUA was assigned with the thorough survey and recording
of the monument. In particular, the project involved the creation
of a variety of products such as: horizontal plans at five
different levels (1:25, 1:50), 26 elevations (1:25, 1:50) — 6
exterior and 20 interior- both in photomosaics and line
drawings, upper views (1:25, 1:50) both in photomosaics and
line drawings, photomosaics (1:5) of all Mosaics on planar or
developable surfaces photomosaics (1:5) of all Mosaics on non-
developable surfaces and a data base (GIS) with detailed
architectural information.
The problem of producing photomosaics of the various details
on developable surfaces (i.e. cylinders, cones etc) has been dealt
with elsewhere (Georgopoulos et al., 2001).
This paper mainly deals with the creation of large-scale
developments of 2™-order surfaces. Although there has been
significant research on this area, it mainly involved grayscale
Images or single image applications. The demand for large-scale
products led to the proposed approach, which is able to
Incorporate a significant number of images.
The application involves:
® data collection for interior work
e the fitting of a mathematically defined surface (in this
case a sphere) to a 3D point cloud
e the procedure followed for the definition of a system
suitable for the projection processes
e the creation of an intermediary model for the one-to-
one correspondence between the points of the surface
of the object and the points of the model surface
e the procedure for the production of the cartographic
developments
The process followed for the fitting of a mathematically defined
surface was based on the relevant articles presented by Faber,
(2000) and Theodoropoulou, (2000).
With respect to the creation of cartographic development, the
application was based on the relevant articles presented by
Theodoropoulou, (1999) and Miniutti, (2000).
However, the core of the process lies within the intermediary
model, which is created with utilization of the DEM. This
model is used during the projection process in order for the
mosaicing of the numerous images of the object to be possible.
Another very significant aspect of the process is the procedure
followed for the selection of a reference system suitable for the
projection.
It should be noted that the whole process was designed and
implemented in the MATLAB environment and it utilizes data
that are always collected within the frame of such applications
i.e. geodetically collected control point coordinates, digital
images and the respective orientations, DEM data etc.
DATA COLLECTION
Considering the demand in large detail, and the high quality of
the final products, the data collection methods were properly
adjusted. All photographs were taken with a Hasselblad camera
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