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2
GENERATION OF A PANORAMA MOSAIC FOR THE DOME OF A PLANETARIUM
Piero de Fazio, Politecnico di Bari, Italy
Josef Jansa, Vienna University of Technology, Austria
email: Josef.Jansa@tuwien.ac.at
KEYWORDS:
ABSTRACT:
Panorama Mosaic, Digital Orthoimage, Geometric Rectification
This paper describes the generation of a panorama mosaic to be projected onto the hemispherical dome of a planetarium,
in particular the Planetarium of the City of Vienna. Digitized amateur photographs serve as input. For the projection of the
pictures eight pairs of off-the-shelf slide projectors of the planetarium (positioned approximately along the equator) must be
used. The main objective of this work is the creation of a homogeneous and continuous panorama projection (as far as both
geometric and radiometric properties are concerned) by means of digital image processing. We assume that perspective
distortions match those of a fictitious observer sitting in the centre of the planetarium's audience hall.
KURZFASSUNG:
Dieser Beitrag beschreibt die Herstellung eines Panoramamosaiks, das auf die halbkugelfórmige Kuppel eines Planetariums
(im kontreten Fall auf die des Planetariums der Stadt Wien) projiziert wird. Als Bilder dienen digitalisierte Amateuraufnahmen.
Für die Projektion der Bilder werden acht Paare von Standard-Diaprojektoren verwendet, die etwa im Kuppeláquator
angeordnet sind. Der Hauptzweck dieser Arbeit liegt in der Herstellung eines homogenen und kontinuierlichen Panoramas
(was sowohl die geometrischen als auch die radiometrischen Eigenschaften betrifft) mit Hilfe der Móglichkeiten der digitalen
Bildverarbeitung.. Angenommen wird, daß sich die perspektiven Verzerrungen für einen fiktiver Beobachter, der sich in der
Mitte des Zuschauerraums des Planetariums befindet, richtig darstellen.
1. INTRODUCTION
The planetarium of the City of Vienna is equipped with a
ZEISS star projector for the projection of star constellations
and with a double ring of eight pairs of standard slide
projectors for accompanying demonstrations. Besides
lectures in astronomic topics the projection hall of the
planetarium is utilized for various presentations in earth and
planetary sciences. In the latter case the standard slide
projectors are also used for projections of circular
panoramas. As the projectors are neither fixed on their
positions nor calibrated, until now the panorama mosaics
were rather approximate with overlaps, gaps, scale and
brightness differences. The geometric distortions were even
quite obvious and annoying due to the eccentric locations of
the projectors and the oblique projection directions.
Figure 1: Star projector (SP), slide pro-
Jectors (P£), and projector's coverage (M)
The given (and in general unchangeable) arrangement of
the projectors is able to cover a 360? zone of the dome
between the equator and the 40? parallel. The remaining
109
zone from some 40? to the pole is currently not covered but
could be included in the mosaic by employing at least two
further (wide-angle) projectors situated near the centre of
the planetarium and pointing approximately towards the
pole of the dome. Figure 1 and 2 show the current situation
in an XY-section and a cross section of the planetarium with
the equatorial slide projectors and their coverage.
z not covered by
a” Équatorial projectors
i
/
Unit Sphere
of Data Acquisition
Sphere of
Projection Screen
P20x id iq
P1Ox 2x
Figure 2: Cross-section of the audience hall,
position of fictitious observer and slide projectors
The main objective of this work is the generation of a
uniform and homogeneous 360? panorama mosaic from a
set of eight photographs (in a panorama arrangement) or
from one single super wide angle or fish-eye zenith
photograph. As mentioned above the current work deals
with the zonal panorama only, without taking into
consideration the coverage of the pole. The double ring of
eight projectors (i.e. 16 projectors all together, numbered as
101 to 108 and 201 to 208 in fiugre 1) is intended to allow
fading and blending. Therefore, the second set of eight
projectors (numbers 201 to 208) covers exactly the same
area on the sperical projection screen, namely the 45? wide
mosaic portions M1 to M8 (see figure 1). The projection
centres of the P20x projectors are some 20 cm above those
of the respective P10x projectors.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996
