International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004
Interna
CRIMES
draw lines on his own intuition, no obvious mathematical definitions could be found.
1. INTRODUCTION
1.1 Background
Between 1420 and 1665, Innsbruck was the residence of one of
Europe's most known imperial families, the “Habsburger”. The
Hofkirche at Innsbruck with the tomb of Emperor Maximilian I
probably is the most important art-historical monument, which
is possessed by the country of Tyrol. It was built between 1555
and 1565 under Emperor Ferdinand I who was the grandson of
Maximilian and the brother of famous German Emperor Karl V.
The cenotaph (i.e. technical term for an empty tomb) with the
statue of the kneeling Emperor is in the center of the church's
nave. The tomb was created by artists from various countries,
who cooperated in the production. It is a unique certification of
European court art, which was influenced by the personality of
the Emperor and its successor as clients. The sarcophagus is
surrounded by 28 more than
embodying ancestors and relatives of Maximilian, the so-called
"Schwarze Mander" (i.e. black men).
The cenotaph itself (fig. 1) has an extent of 6,4 m x 4,5 m x 3,3
m and consists of a frame of black marble in which the 24
reliefs of white marble (each approx. 80 cm x 45 cm) are
embedded in two horizontal rows. These reliefs show scenes
from the life of the Emperor Maximilian I. They have a level of
detail within the range of 0.1 mm and had to be documented in
particular and with highest precision available. On the cover of
the tomb, the kneeling figure of the Emperor is central,
surrounded by representations of the four basic virtues, which
are arranged at the four corners. All mentioned figures are made
of dark bronze.
1.2 Restoration
On the occasion of the preservation and restoration of the tomb,
a complete art-historical and geometrical documentation was
initiated for the first time since the completion around the year
1568. In order to allow a continuous access for tourists, only
one half at a time was concerned by the measures of restoration
and covered in a boarding. The other part remained accessible
for the public. The cenotaph was separated for centuries by a
wrought-iron lattice from the visitors. Additionally the white
reliefs were hidden by glass plates. In May 2002 the right half
Different methods can be used to visualize the meshed surface model. Line plots from the photogrammetric stereo models do not jail
really give an adequate representation of this object. 3D visualization using the scanning results can achieve a much better 60 hou
impression of the complicated geometry after data modeling, error correction, and filling in remaining ‘holes’. In order to model the is not:
complex geometry, it is necessary to use huge amounts of data. The model in its highest resolution consists of more than (stand:
1.000.000.000 triangles. Because of restrictions in the hard- and software presently available, the high resolution model has to be correct
processed and stored in more than 140 separate virtual models. The project proves the enormous potential of these new technologies,
but shows as well that more progress is needed in hardware and software development to accomplish such demanding tasks. Becau:
An attempt was made to convert the meshed 3D models to 2D vector drawings, similar to those resulting from traditional plotting sary tc
using photogrammetric stereo models. Solutions could be found to select all object outlines and all edge areas where curvature GOM
shows high absolute values. On the other hand, for other “lines” (e.g. the details of a human face) where a stereo plotter operator will fringe
the res
versio;
selecte
2. DATA ACQUSITION millior
2. General remarks se
The setting of tasks was not clearly defined — as it is often the
case in comparable projects, and had to be developed in co-
operation with the responsible authorities. It stood firmly that
the rare chance of accessibility from all sides should be used for
documentation by all means. Of course, neither detailed plans
nor art-historical documentations of this tomb were available at
this time. Because of the preciousness of the object - and the
uniqueness of the opportunity for data collection - accordingly a
combination of geodetic measuring methods was suggested and
carried out in May 2002.
On the one hand classical close range photogrammetry was
used for the complete measurement of the cenotaph and on the
life-sized bronze figures, other hand - due to the complex 3D details of the reliefs — the
documentation should be carried out by use of 3D scanning
devices. The appropriate scanners were chosen from a list of
available instruments (i3mainz, updated 2004). The geometrical
survey of the object by the scanners also later would be
combinable with the radiometric information from the photos
when both methods were used in one operation. The
measurements were accomplished by three independent teams.
In order to avoid interference during the short time available, all :
measurements had to be coordinated exactly and scheduled
accurately in advance. $1
: : Data |
Since the surveying methods for the geometric documentation was
of the cenotaph have been described in earlier publications CU
(Marbs 2002, Hanke 2003), only a brief outline is given in the an
following sections. eut
: : o one d
2.2 Geodetic survey and photogrammetric densification ihe d
A general requirement for all surveys was a common coordinate resol
reference. A precise network of eight observation points around ean t
the cenotaph was established and vertical and horizontal angles (DI
were observed to the reference targets on the object for the Sh
scans and for the photogrammetric images (spheres and self- relief
adhesive flat targets). An accuracy of better than 0.5 mm detail
(standard deviation of spatial location) could be achieved. $3
Additional targets which were necessary for the detail scans of filin
was completely restored and it became necessary to dismantle
and transfer the temporary housing set up by the restoration
technicians to the other side. Thus, for ten days for the first time
since its establishment the cenotaph was accessible from all
sides and unwrapped both from lattices and from windowpanes.
This time slot was used for the complete documentation and the
measurement work described here.
the reliefs were stuck onto transparent adhesive tape which was
fixed in front of the reliefs without touching those. The The
coordinates for those targets were derived by photo iT
triangulation using GOM's widely automatic TRITOP system.
2.3 3D Scanning
A complete scan of the cenotaph was achieved with a MENSI
S25 triangulation type laser scanner. A point density of about 2
