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New perspectives to save cultural heritage
Altan, M. Orhan

Heinz Rüther 3 , Gerard Mtalo b , Eric Mngumi “.a
3 School of Architecture, Planning and Geomatics, University of Cape Town - (Heinz.ruther@eng.uct.ac.za)
b University College for Land and Architectural Studies, Dar es Salaam - (mtalo@uclas.ac.tz)
CIPA 2003 XIX th International Symposium
KEY WORDS: African Heritage, Kilwa, Digital Documentation, Laser Scanning, CAD, Data Structure
No metrically correct 3D documentation exists for the UNESCO World Heritage Site of Kilwa Kisiwani and Songo Mnara, once one
of the most important African trading centres in the Indian Ocean region. Modem technology makes it possible to create such
documentation and develop an integrated information system for the site. This paper describes an ongoing research project on the
documentation of two of Kilwa’s remaining structures, the fortress, known as Gereza, and the Great Mosque on Kilwa Kisiwani. The
project forms part of the development of a methodology for the digital recording of African heritage sites and the design of a
database as part of an integrated information system for African heritage sites. The Kilwa documentation is a pilot- and case study
within this larger framework. It focuses on the development of appropriate methods, procedures and techniques, recognizing the
technical, economical and physical limitations of documentation work in an African environment. Specifically, the project looks at
the smooth transfer of photogrammetrically acquired point clouds into CAD programmes. The photogrammetry-to-CAD transfer is
addressed through the development of a data structure, which is employed to systematically code photogrammetrically acquired
points on features of interest. An interpreter is then used to translate the labels of the feature points and their coordinates into an
AutoLisp feature file, which in turn can be ‘understood’ by the CAD system and plotted. The resulting 3D wireframe model forms a
basis for the creation of surface and/or solid models that are subsequently draped with real texture for realistic representation of the
site. The paper also reports on first experiences with a laser scanner and attempts a comparison of laser scanning and close-range
1.1 Back ground and motivation
The coast of East Africa, from Mogadishu to Mozambique has
several small offshore islands and mainland settlements with a
history dating back to early medieval times. It is important for
indigenous people of East Africa to realise, that the popular
theory, that these ruins are exclusively of Arabic origin, is
erroneous and possibly a deliberate attempt to obscure the
predominant East African element in the history of the region.
The structures are understood today as the relics of earlier
Swahili settlements, and not those of foreign migrants or
invaders (‘Arabs’, ‘Shirazi’ and others), as often maintained.
Although the mosques and tombs are by definition Islamic, they
are not direct transplants from Arabia or the Persian Gulf.
Instead, their architectural style has developed locally and is
unique to the Swahili coast in both forms and coral masonry
techniques (J.E.G. Sutton, 1998).
The ruins of Kilwa are the remnants of a once prominent
trading centre in East Africa, with links to Sofala and
Zimbabwe, to the South, and Arabia and the Far East to the
North and East. Its merchants traded gold, silver, ivory, pearls,
perfumes, Arabian crockery, Persian earthenware and Chinese
porcelain. In recognition of its importance, UNESCO declared
Kilwa a World Heritage Site in 1981 and the site also appears in
a list of the 100 World’s Most Endangered Heritage Sites. The
site comprises a number of buildings distributed over two
islands, Kilwa Kisiwani and Songo Mnara. The Gereza, a
fortress, (Figure 1) and the Great Mosque of Kilwa (Figure 2),
two of the most prominent buildings of the site and the objects
of the documentation, are located on Kilwa Kisiwani, in sight of
the coast of Southern Tanzania. Ground plans of the Gereza and
the Mosque have been published before, but no metrically
accurate 3D documentation of the Kilwa ruins exists. It was
therefore decided to include Kilwa into the African Heritage
The digital documentation of the Gereza, including 3D models,
database and GIS is designed to
- create a permanent digital record of the Kilwa ruins
- provide metric data for ongoing restoration work
- provide data for education and research
- generate awareness of African Heritage in Africa
- support initiatives towards the development of tourism
- contribute to the development of an appropriate
methodology for African heritage recording, with the aim
of creating an African (architectural) Heritage Database and
Information System (Rüther, 2002).
In developing the documentation a number of factors specific to
Kilwa and Africa had to be considered:
- the extent of deterioration of the Gereza is such that most of
the building has been reduced to an open structure with a
number of freestanding walls without a roof, while about
50% of the mosque is roofless. The top sections of the
freestanding walls are badly broken and highly irregular